Troubleshooting Professional Magazine
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Automotive Cooling System Maintenance and Repair |
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Those two years also brought bushels of email containing voluminous information about automotive cooling systems. I've learned a lot in the past two years, and I'd like to share some of that knowledge with you.
This issue of Troubleshooting Professional Magazine explores the details of automotive cooling systems -- how they work, how to maintain them, and how to diagnose them. This issue serves three audiences:
And that's why this issue of Troubleshooting Professional is so important to car owners. If your local shop doesn't understand the role of a broken head gasket as a cause of overheating, or the fact that such a broken head gasket might not exhibit the classic symptoms of steam out the exhaust or white/yellow foam/gunk on the oil cap, you probably want to look for a different shop. Also, the car owner needs to understand the cost of overheats (often exceeding $2000.00), and the fact that the single most important protection against overheats is preventive maintenance.
The do it yourself mechanic will appreciate the diagnostic and preventive maintenance information in this magazine. This information will eliminate most unnecessary parts purchases and unneeded labor by enabling more accurate diagnosis.
So if you fix cars for a living, fix your own car, or just own a car, kick back, enjoy, and profit from this magazine.
Do you think this is a good idea for a book? What information would you like to see in the book, and how would you like to see it presented? Do you have any suggestions?
In no event unless required by applicable law or agreed to in writing will the copyright holder, authors, or any other party who may modify and/or redistribute the information, be liable to you for damages, including any general, special, incidental or consequential damages or personal injury arising out of the use or inability to use the information, even if such holder or other party has been advised of the possibility of such damages.
The information you see in this document is my opinion, based on personal experience, experiences reported by Troubleshooters.Com visitors, and research. It wouldn't surprise me to find that some of the information in this document is erroneous. If you choose to use this document's information, you should use it in addition to information from other sources.
Be careful not to short the battery -- battery explosions can throw potentially burning/blinding acid. Don't open the radiator cap of an overheated car. When it's cool enough to open, use a rag to block any spray, and open very slowly. Wear hard shoes capable of shielding impact from a dropped part.
Take proper precautions when jacking up a car so the jack doesn't "kick out". A "kicked out" jack can be every bit as destructive as a kick from a large horse. Block the wheels, put on the brakes, seat the jack properly. Never crawl under a jacked up car unless it has been properly blocked up and completely secured. Even then, remember that earthquakes, sudden wind and drunk driver impacts happen. A professional lift is always best.
The preceding warnings are by no means an exhaustive list of the risks encountered when working on a car. Always use common sense. You assume full and complete responsibility for the use of the information on this page.
This isn't just theory. An old skating buddy lost a finger when his wedding ring was grabbed by a fan belt. I met a guy at MacDonalds who spent 2 weeks in the hospital when an open-carb backfire caused third degree burns over most of his forarm. Skin graft city. Imagine if his face had been by that carb. We've all read about people who crawled under a jacked up car and got crushed.
Be very careful, or else do not work on cars.
The cooling system works by moving coolant (water plus antifreeze) through the engine, and moving that heated coolant through the radiator, where its heat is transferred to the surrounding air. The cooling system must have enough cooling capacity to cool a car ascending a long, steep mountain road, where the driver might have the gas pedal 2/3 of the way to the floor.
But it must be regulated in such a way that at a steady 40 MPH on a flat road in subzero weather, the engine's temperature is allowed to quickly rise to the manufacturer's recommended temperature (usually about 200 Farenheit, give or take 20 degrees). That recommended temperature should also be maintained when the car goes up a 10 mile 7% grade in 100 degree weather. Such regulation is accomplished by the car's thermostat -- a heat sensitive valve that allows coolant to flow through the radiator at high temperatures, but cuts off that flow at low temperatures.
The water pump sucks cooled coolant from the radiator and pushes it into the engine. The coolant flows through the engine, absorbing the engine's heat. If the thermostat is open, that coolant then flows into the radiator for cooling. As it flows through the radiator, it heats the tubes and fins on the radiator, and that heat is transferred to the air flowing through the radiator. At low speeds that air flow is maintained by the fan, and at high speeds it's maintained by the relative velocity of the vehicle in relation to the outside air.
Meanwhile, a parallel path brings hot coolant from the engine through the heater in the passenger compartment, and back into the water pump. That path is controlled by the heater valve, which in turn is controled by the lever or electronic climate control on the dashboard. The parallel path is not restricted by the thermostat, so passengers get heat even when the thermostat is closed. However, some cars have a mechanism which shuts off coolant through the heater during an overheat, I guess on the theory that you want to maximize flow through the radiator by shutting off the heater. While such a theory might be credible when the cause of overheating is low coolant, it prevents the alert driver from turning on the heater full blast and thereby letting the heater act as a second radiator. Perhaps such a shutoff is a safety feature so there's no way overly pressurized coolant can rupture the heater and spray on the passengers. So if you've had symptom where "the car overheats and then the heater blows cold air", the heater probably has been shut off due to overheat.
The entire system is sealed with one exception. The radiator cap contains a spring which maintains a constant pressure by venting coolant (to the reservoir tank) when pressure rises above its specified value -- typically around 15 PSI. It's normal for some coolant to vent in this way, which is why the reservoir is more full when the car is hot than when it's cold. The radiator cap also allows the vacuum created when the system cools to "suck back" coolant from the reservoir. But in the case of an extreme overheat, vented coolant overflows the reservoir, thereby creating a low-coolant situation and making the overheat even worse.
Looking at the diagram, you see that oil, gasoline, combustion gasses and coolant all flow inside the engine. These materials are kept separate by the head gasket(s). A breached or broken head gasket, or a bent head, allows any or several of these materials to mix. Coolant into the cylinders produces huge clouds of white exhaust (steam) out the tailpipe. Coolant into the oil produces a yellow/white foam or gunk on the oil cap, as well as degrading the oil, possibly past the point of lubricating usefulness. Combustion gasses leaking from the cylinder to the coolant might produce no obvious symptom, but it's an extremely dangerous condition, because it can cause an overheat by any one or more of four different mechanisms:
Your cooling system must be able to get rid of all that heat. Difficult enough, it becomes even more of a challenge if the air temperature is warm (less heat transfer from radiator to air), and brutal if your car is heavily loaded or towing something. If the heat generated by combustion significantly exceeds the cooling capacity, you'll severely overheat quickly (typically after a mile or two of climbing).
A well functioning cooling system has the capacity to maintain the engine
at under 100 degrees temperature during continuous 50mph level drives on
cool days. But of course the temperature needs to be 160-230 Fahrenheit,
depending on the car (consult your owners manual). That means in most driving
situations the cooling capacity must be partially defeated. This is accomplished
by the thermostat, which acts as a deliberate bottleneck, regulating the
amount of cooling to keep the temperature at a proper level. A somewhat
typical thermostat would be closed until 180 Fahrenheit, after which it
would open further as the temperature increases, until at 195 it's completely
open. This means that in the 15 degrees between 180 and 195, the cooling
capacity would go from 0 to the full capacity of the system (enough to
scoot up a long 6% grade at 65 mph carrying 5 people in a well designed
and maintained machine). Below is a graph showing how temperature increases
with increased engine heat production (i.e., more gas):
The portion in blue represents a level of heat production so small
that it can be disbursed by the direct contact of the engine with ambient
air. In practice this might be achieved in the case of a 40mph wind blowing
into the open hood of a car idling in the deep of a northern Minnesota
winter's night, but otherwise this condition is never seen in real life.
An idling engine, and certainly driving, at anything resembling normal
conditions requires radiator cooling.
| NOTE: Don't make the mistake of thinking the preceding diagram represents temperature versus time. While that graph would look similar at the leftmost part of the graph, that's not what's being represented. You can think of the preceding diagram as a graph of various driving conditions, each maintained for 10 minutes or more. |
The violet portion represents heat production levels within the regulated cooling capacity of the cooling system. The slight temperature gain across this range is due to the fact that the thermostat opens slowly and steadily over a range of about 15 degrees Fahrenheit. This is the normal operating range of the vehicle. Once the engine is warmed up, all driving should be done in this range.
The red portion represents a heat production level beyond the cooling capacity of the cooling system. The temperature goes sky high. On a well maintained vehicle, you would expect the red portion only when the car is used beyond its design capabilities, like using a compact car to pull a trailer up a long 6% grade.
The bottom line is that on a well maintained vehicle, the bottleneck,
by a huge margin, is the thermostat. Contrast that with a vehicle with
a compromised cooling system not capable of cooling a hard worked engine,
or in extreme cases even a lightly worked engine:
Here there's no regulation. The entire graph is basically a straight
line. Moderate hard usage sends the car into the red. The operating temperature
of a vehicle in this state of repair would vary widely with ambient temperature
and length of time driving. Typically no "normal operating temperature"
can be identified for a vehicle in this condition. Such a vehicle will
almost certainly experience a catastrophic overheat the first time the
driver takes a lengthy drive, or drives in hot weather, or drives up a
moderate hill.
The controlling bottleneck of this vehicle is not the thermostat -- it's something else in the cooling system. The automotive technician's task is to find that bottleneck.
Sometimes you get lucky and an overheat can be corrected by fixing its root cause. But all to often, overheating -- even a single 3 minute incident -- can cause consequential damage that costs thousands to fix. An overheat is a very bad thing.
The most common consequential damage is a broken head gasket. This happens when the head and block expand differently than the head gasket, or even worse, when an aluminum head and a cast iron block expand at radically different rates, breaking the head gasket. Bimetal engines, whether they be aluminum heads on a cast iron block, or cast iron heads on an aluminum block, are likely to break head gaskets with the slightest overheat. Unfortunately, replacing head gaskets is a big job requiring hours for even an experienced mechanic with all the right tools. For a do it yourselfer, it could be prohibitively time consuming or even impossible. As a result, the cost of replacing a head gasket ranges from $500.00 to $2500.00, depending on the make and model, and whether the heads must be machined.
Broken head gaskets result from a moderate overheat, or even a mild overheat on a bimetalic engine. A more serious overheat can bend or break the heads. Now you have a large parts cost to add to the huge labor charge for replacing the head gasket(s). New heads cost hundreds, and machining heads is also costly.
Some folks consider continuing to drive the car with a broken head gasket. That's a very bad idea if you want to keep the car more than a year. Combustion gas in the coolant can easily cause even more severe overheats, plus it can quickly cancel the anti-corrosion properties of your antifreeze, leaving you open to corrosion, leaks, and blockages, all of which result in further overheating. If coolant gets into the oil, the oil's lubricating ability is compromised, leading to engine seizes, bearing freezes, and all sorts of other problems. If coolant gets into the cylinders it can cause a broken starter, solenoid, or flywheel. Broken head gaskets often make the car run poorly, and often make it a gross polluter, which can be costly indeed in states that enforce smog regulations.
Your engine was designed to operate at a certain temperature. When it operates colder than that, emissions go up, efficiency goes down, and engine wear increases. This is why cars don't drive as well cold as they do when they're "warmed up". On the opposite end, cars operating hotter than designed, even at temperatures lower than what it would take to break a head gasket on a cast iron block/head combination, risk pre-ignition/detonation caused by too-high engine temperature. Such pre-ignition/detonation can damage various components in your engine. If you've ever driven a seriously overheated car you know it sounds much different, and it doesn't sound good.
But what if you're one of these wild and crazy guys who doesn't shut down the car even when the temperature gauge is pinned, there are huge clouds of steam coming out the hood, and the car has started running funny. You, my friend, will most likely need a new engine. Extremely overheated engines seize, freeze, warp, and who knows what else. Engines aren't too expensive, but the labor is prohibitive, and all too often the new engine lasts 10,000 miles and then blows up.
Added to those costs is the cost of having an unreliable vehicle. Cars that overheat once tend to overheat often; unless an unusually competent and comprehensive repair job is done. Overheats results in a tow charges, missed work, and even hazards to personal safety. It's doubtful anyone's personnel record lists "broken head gasket" as a cause for job termination, but it just might list "excessive absence" and "unreliability".
I hope I've gotten your attention. A single overheat can cost you thousands. You need to know that, because during the rest of this magazine I'll be recommending preventive maintenance that costs nearly $100.00 per year, and diagnostic procedures which cost almost $100.00 not counting the actual fix. When evaluating the cost of my suggestions you must realize the cost of the alternatives -- $1500.00 to fix a head gasket, $300.00 for a new radiator installed, and if you go to an incompetant Automotive Technician who practices diagnosis by serial replacement, you'll spend even more.
When viewed alongside the alternatives, $100.00/year to keep your cooling system healthy starts sounding downright cheap.
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Considerable documentation on the web and in other places states that an overly lean fuel mixture can cause overheating, so you might want to check your mixture. That being said, I can tell you that my 1973 Ford Country Squire ran incredibly lean (former owner's smog workaround) and yet did not overheat. |
In addition, many used cars have insufficient cooling capacity because somebody cut corners when replacing a radiator. I once bought a Dodge Coronet with a radiator salvaged from a Dodge Dart. On hot days the slightest hill would overheat it. I had a radiator shop make and install a huge custom 4 row and it no longer overheated. Some used cars lack cooling capacity because the fan shroud has been removed. Such cars tend to overheat more at idle and low speed.
If you've proven to a reasonable degree that the car's cooling system,
as manufactured, is insufficient to cool the car during extremely challenging
driving, see if you can install a higher capacity radiator. Install the
highest capacity radiator you can purchase or have manufactured.
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When replacing a radiator, it's best to use a similar type of radiator, but bigger. For instance, if the original radiator was aluminum, it's best to make the new radiator aluminum. Try to replace plastic radiators with bigger plastic radiators. If you need to use a different type replacement, be aware that you might need to change the type of antifreeze you use. |
When researching low coolant it's important to discover where the coolant is going. It's either leaving through the radiator cap or reservoir, or it's not. In either case, there are various mechanisms:
Here are some of the mechanisms of inadequate heat transfer:
So with the car running and warmed up (but not overheated), visually
inspect the hose and make sure it's not collapsed. With the car not running
and the engine cool, feel the hose and make sure it's incompressible with
your fingers. Also make sure it's not cracked or brittle.
Although a collapsed bottom hose would cause an overheat, it's possible that a massive radiator blockage caused the collapsed hose. If you see a collapsed hose and it appears to have been the correct hose (i.e. it has a spring but the spring failed), look very carefully for blockages in the radiator. Whatever the cause of the collapse, replace any bottom radiator hose that has ever collapsed, and be sure to fix whatever caused the collapse.
Most radiator deposits serious enough to push the temperature anywhere near redline are visually observable if you drain a few inches of coolant from the radiator. Other diagnostic tests include using an infrared temperature sensor to detect "hot spots" in a radiator. Such hot spots indicate places that are cooling efficiently (the hot coolant is flowing through them), as opposed to the "cool spots" that have no coolant.
You noticed I said replace the radiator, not "rod it out". I'm of the opinion that oftentimes "rodding out" does not cure the problem, and in many other instances it cures the problem for only a few months. "Rodding out" is labor intensive and not cheap. The extra money spent on a brand new radiator is money well spent in my opinion.
And in my opinion, there's no such thing as too much radiator. Get the biggest one you can. A huge radiator can, in some cases, compensate for suboptimal conditions:
If you're a car owner, upon hearing that your current radiator is seriously
corroded, deposited or plugged, I'd advise getting the biggest possible
radiator. If you need to spend extra money to have a huge radiator manufactured,
that's a good idea, assuming you have confidence in the outfit doing the
manufacturing.
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When replacing a radiator, it's best to use a similar type of radiator, but bigger. For instance, if the original radiator was aluminum, it's best to make the new radiator aluminum. Try to replace plastic radiators with bigger plastic radiators. If you need to use a different type replacement, be aware that you might need to change the type of antifreeze you use. |
If you're an Automotive Technician, try to get your customer to see
the value in a huge, brand new radiator.
You can deduce when a thermostat opens by a number of means, including feeling for pressure changes on the upper hose, or viewing water flow through the radiator. SUCH VIEWING SHOULD BE DONE IN A SAFE WAY -- warm but not hot, eye protection, do not lean over the radiator.
Once you can determine the opening and closing of the thermostat, measuring the engine temperature with a thermometer can tell you the opening temperature. I've never measured the temperature this way. Many techniques exist, but I can't vouch for any particular techniques.
Thermostats typically malfunction by one of two mechanisms:
Many people have successfully cured gas bubble problems by drilling a 1/8" hole in the thermostat. This hole lets the gas rise past the thermostat, allowing the thermostat's wax temperature sensor to once again contact coolant. However, it's possible that such a hole could cause some problems, so you might want to weigh that possibility.
Here are the instructions one Troubleshooters.Com visitor, A.S.E. certified
master truck and auto mechanic Dennis Buler, gave me for drilling the 1/8"
hole:
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Top view of thermostat. The violet dot at the 12 o'clock position of the rim is where Dennis recommends drilling the 1/8" hole. |
| Side view of thermostat | |
| Bottom view of thermostat |
Dennis' exact words were "i drill the hole in the flat disk part like half way between where the gasket would seal and the center opening mechanism".
One more thing. Remember that a gas bubble can be caused by combustion
gasses passed through a head gasket breach. In such a case it's likely
you'll need to replace your head gasket.
At temperatures below the boiling point of water, water is more effective at absorbing and carrying heat than any mixture of water and either ethylene glycol or propylene glycol. If you have a 160 degree thermostat and your cooling system is functioning well, you could theoretically add cooling capacity by replacing your water/antifreeze mixture with pure water.
But the added cooling capacity would be short lived indeed. Adding antifreeze gives the following benefits that water alone cannot:
Always know what you're using for coolant. If you know there's no propylene glycol in the coolant mixture, you can use a simple specific gravity indicator to deduce your mixture. The ideal mixture is 50/50, but in extremely cold climates you can get by with 70% antifreeze and 30% water. Any more antifreeze will lead to overheating.
If there's a likelihood that some or all of your coolant is propylene glycol, specific gravity measurements will not accurately indicate your mixture. Use a refractometer instead.
If the coolant is so old that the driver does not know what all is in it, perhaps it's time to flush the cooling system and replace it with whatever the car's manufacturer recommends. Coolant is discussed in more detail later in this magazine.
Most cars with forward facing engines use a mechanical fan system, consisting of the fan, fan clutch, fan belt, and radiator shroud. On such a system the fan belt turns the fan clutch, which turns the fan, which pulls air through the radiator, constrained by the radiator shroud.
If the fanbelt slips, it can't deliver necessary torque to drive the fan at sufficient speed, and idle/low speed overheating can result. The fan clutch is designed to deliver more torque at higher temperatures. If it doesn't function right, it doesn't transmit enough torque to drive the fan at sufficient speed, and idle/low speed overheating can result. The fan shroud is like a tunnel between the fan and the radiator, ensuring that all air pulled by the fan comes through the radiator, instead of simply being sucked from the surrounding area or around from the back of the fan. Without a fan shroud, idle and low speed overheating is likely to occur.
You might wonder why a fan shroud is necessary on a mechanical fan when it's not necessary on an electrical fan. An electrical fan is mounted to the radiator itself. It's very close to the radiator, and moves with the radiator. Contrast this with the mechanical fan, which must be mounted several inches away from the radiator. Because the mechanical fan moves with the engine, and not with the radiator, installing the mechanical fan close enough to eliminate the need for the fan shroud would cause the fan to gouge the radiator when extreme engine torque causes the engine to move. This is especially true when a motor mount is broken.
Bugs, dirt and debris can clog the air flow passages of your radiator, or of the air conditioner cooling coils before the radiator. Either way, airflow is restricted, and overheating can result. There are methods of cleaning the radiator and cooling coils, but be very careful not to damage the delicate tubes and vains. Also, these areas are often difficult to access. Sometimes compressed air is the best way to clean them. Once cleaned, you might want to install a "bug catching net" in your grill, especially in climates where there are numerous flying bugs.
Radiators are typically constructed with tiny tubes soldered to fins, or else oval tubes. Either way, the idea is to allow air to flow through the radiator. If these things become bent, air flow is impeded. Bent tubes and fins can be straightened, but trying to do so can also further damage the radiator or cause a leak. Radiators should be handled delicately.
Another impediment to air flow is a damaged radiator. Vains and tubes are bent and twisted by crashes and mishandling of the radiator by inept technicians. Another cause of radiator damage is fan damage, in which a mechanical fan hits the radiator. The primary cause of fan damage is a bad motor mount, so always maintain your motor mounts.
In general, you might deduce impediments to cool air by observation, or lacking that by seeing how well compressed air goes from the outside of the grill to the area between the radiator and the engine. On my 1988 Buick Park Avenue with air conditioning, when I put the blowing end of a 5HP industrial vacuum on the grill, I could feel the breeze on my hand inside the engine compartment, but just barely. If you have an easy way of removing your grill, perhaps the best and quickest test is to investigate is visually. Even if the air conditioning cooling coils block your view of the radiator, it's a good bet that if the air conditioning coils are clean, so is the radiator.
A complete radiator investication involves removal of the radiator, which is labor intensive and should only be done when there's good reason to strongly suspect dirt on the radiator or bending of the radiator's components.
Another extreme unlikelihood is that the water pump is pushing flow backward, so that there's suction on the upper hose. This could conceivably happen if a water pump made for a serpentine belt is used with a belt off the crankshaft, or vice versa. Reversed pump direction would likely cause other strange symptoms.
That being said, the water pump's job is to circulate coolant through a well functioning system, not to brute force coolant through a radiator whose tubes are clogged with deposits. There's no easy and accurate way to assess the level of water pump functioning. Here are some things that can go wrong with a water pump.
An undersized or oversized pulley can be deduced by obtaining the manufacturer's documentation, or by comparing the pulley to what the manufacturer put in similar cars. Be sure the similar car is similar enough. For instance, if your water pump is driven by a serpentine belt, make sure you compare it to a similar model and year with a serpentine belt. An oversized pulley causes the pump to turn too slowly, thus reducing coolant flow, possibly to the point of overheat. Note that theoretically the overheat should be speed independent because high speeds require faster coolant flow. But that's just theory.
One might think that an undersized pulley would cause the pump to spin faster, thereby increasing coolant flow. While this may be true for a moderately undersized pulley, if the pulley is significantly undersized it's just as likely to present so much torque, and so little traction area, that the belt will slip, causing a vast decrease in coolant flow -- probably at high speeds where coolant flow is most crucial.
Because internal blockages in the engine block or heads are so hard to diagnose, it's best if they never happen. Practicing corrosion protection and impurity protection is probably your best defense.
This section discusses four lower level causes, as well as their ultimate causes and effects. Those three lower level causes are:
Corrosion happens when the coolant loses its anticorrosive properties. With standard antifreeze in a 50/50 mixture this happens in about 2 years or 24,000 to 30,000 miles. Same with 50/50 propylene glycol or 100% propylene glycol. There are several "extended life" antifreezes. Some, such as the GM "Dex-Cool" complient antifreezes (Texaco/Havoline Dex-Cool and Prestone Extended Life 5/150), are designed to go 5 years or 150,000 miles between changes. Many new GM cars come from the factory with this type of coolant. However, "long life" coolants often revert to 2 years when mixed with other types of coolants, or when used in a system with trapped air or rust/corrosion. Mixing antifreezes is generally a bad idea, and certain combinations can actually promote corrosion.
Furthermore, encroachment of combustion gasses into the coolant via a head gasket breach can neutralize any coolant's corrosion inhibition long before the specified life.
Most antifreeze is extremely cheap. My local Discount Auto Center sells Prestone brand Ethylene Glycol standard antifreeze for $6.99 a gallon, and Havoline Dex-Cool for the same price. You can get 3 gallons of high quality ethylene glycol antifreeze for $21.00. Propylene glycol is less likely to poison animals and is a little more costly, as are the various more exotic antifreezes. In my opinion, it's time flush and change your antifreeze when:
While we're on the subject of economics of corrosion protection, distilled water is just too cheap not to use, assuming you're a car owner doing your own work. Distilled water costs about $0.70 per gallon, so for about $2.00 per year you can give the anticorrosives in your antifreeze a fighting chance by not introducing calcium, lime or who knows what into your cooling system. This is especially important if your antifreeze uses phosphates as a corrosion inhibiter, because phosphates react with calcium to produce radiator-clogging scale. Naturally, if you find yourself low on coolant and need to get home, use tapwater. Never use softened water, as it contains salts that can quickly corrode your cooling system.
If you can conquer the corrosion monster, you're most of the way to making sure your car never has a single incident of overheating.
The sad thing is that most people won't spend the money. Two cents per mile doesn't sound like much, but when you spend it all at once, and when you're spending it on a car that seems perfectly healthy, many folks feel it doesn't make much sense. If you're an automotive tech, your job is to explain why it does make sense. Explain that the customer's car may only seem healthy. Cooling system problems are a disease with a long incubation period. It can take 4 years for radiator corrosion and deposits to reach the point where they compromise everyday driving.
But once the symptoms appear, they're often relentless. That clogged radiator, if not replaced in time, can lead to a head-gasket busting catastrophic overheat. And if the head gasket isn't diagnosed correctly, replacing the radiator doesn't completely eliminate the symptom. The customer begins to believe his car is possessed by the overheating demon.
The radiator isn't the only component being compromised. Old coolant corrodes the water pump, leading to failure. And you know how replacement water pumps are -- they're seldom as good as the original, so after the first replacement, water pumps become a regular maintenance item at a couple hundred a pop.
An undiscovered bad hose can break, and unless the car's driver has the sense to safely pull over and shut it down immediately, the head gasket will be breached.
Check your motor mounts often. A broken motor mount can allow a mechanical fan to slice into the radiator. This can render the vehicle undriveable, or it can simply reduce the excess cooling capacity to the point where the vehicle will overheat in challenging driving conditions.
Preventive maintenance can't necessarily prevent all these problems, but it can usually postpone most of them until well past the car's first decade, and such preventive maintenance makes it likely that any cooling system problems will be caught before heads or head gaskets are damaged.
This article contains an example of a cooling system preventive maintenance program. I'd imagine it costs about two cents a mile, and will probably enable the cooling system to be problem free for its first decade, and limit problems to minor repairs thereafter.
If I ran an automotive shop, I'd package the yearly, two year and three year maintenance items for a fixed price, and sell them to customers as peace of mind. It takes a little education, but it's worth it in dollars and cents and in customer goodwill. Note that much of this maintenance overlaps other maintenance, such as oil and lube and transmission, so it could be combined with those. Finally, by keeping track of the customer's maintenance, the shop can provide a valuable service to customers with better things to remember than exactly when they last replaced their thermostat or belts. Also, by providing that service, the shop can maximize the likelihood that the customer will use the shop for all work, and not grind for the lowest price.
| My car overheated , so I took it to the shop. They replaced the thermostat. I drove it for a few days and it overheated again. They then charged me another $200 to replace the water pump, but as soon as I got the car home it overheated so badly that it wouldn't even start. This time they rodded out the radiator for $150, and it got better, but still overheated. So they charged me another $200 to replace the radiator with a new one (and told me they were giving me a break on the price). That improved the situation even more, but it still overheats on long trips, and it runs rough and there's a lot of white smoke coming out the exhaust. When I took it back to the shop they said it was a broken head gasket, and it would cost $1200 to fix. What do I do? |
It's entirely likely that the original root cause was the radiator,
and nothing but the radiator. But during the time consumed by diagnosis
by serial replacement, successive overheats broke the head gasket, thereby
adding yet a new overheating cause. Or take the case of an even less competant
shop:
| My car overheated, so I took it to the shop. They replaced the thermostat, but it still overheated. They then charged me another $200 to replace the water pump, but nothing changed. So they replaced the radiator, but everything was still as bad. Yesterday I took it to another shop, who told me the white foam on the oil cap and steam coming out the exhaust indicates a broken head gasket, which was caused by all the overheating. And they told me I have a collapsed lower radiator hose, which probably caused the original overheating, and that the cost to install a replacement hose would have been $50. Could this be true? |
Diagnosis by serial replacement is NOT an option if you want to have a profitable shop over the long term. Although some components are hard to test (water pumps, for instance), enough easy tests are available that you can usually pinpoint the root cause if you do all the simple tests. Another reason to do a full scale diagnostic workup is that by the time you see a typical overheat, multiple causes may be at work.
The following outline lists and categorizes relatively cheap and simple
tests that will maximize the probability of accurately identifying the
root cause, thus preventing costly and credibility busting diagnosis by
serial replacement:
Automotive coolant is a mixture of two liquids:
Propylene glycol/water mixtures have the disadvantage of not being measurable with a traditional specific gravity measurement tool. Instead these mixtures must be measured by the much more expensive refractometers. And, as previously mentioned, at all but the most concentrated mixtures, ethylene glycol solutions are more efficient coolants.
"Ordinary" antifreezes use ethylene glycol as their freeze inhibitor.
"Environmental" antifreezes use propylene glycol. Most of the new "long
life" antifreezes use ethylene glycol. They derive their long life from
their corrosion inhibitors, not from a special freeze inhibitor.
Ordinary "2 year" antifreezes use borates, phosphates and/or silicates as corrosion inhibitors. Most North American standard antifreezes contain phosphates, which are great at corrosion protection, but can react with calcium in tap water to produce radiator-clogging sentiment and scale. The harder the water, the more of a problem this becomes. If you change your own coolant, you can avoid this by using only distilled water. At less than a dollar a gallon, it's a bargain.
Never use softened water in a cooling system. Softened water contains salt (NaCl), which becomes conductive in water and turns your entire cooling system into a battery, destroying first your aluminum parts, and then going to work on even the cast iron.
The new "extended life" antifreezes are the same as conventional antifreezes except for their corrosion inhibitors. Most "extended life" antifreezes use organic acids instead of inorganic salts (borates, phosphates and silicates) for corrosion protection. When used correctly, these organic acids are said to protect against corrosion for up to 5 years and 150,000 miles. There have been a few reports of problems with corrosion on lead-soldered copper/brass radiators protected with organic acids, and also a few reports of sludging with organic acids. These are discussed in more detail in some of automotive author Larry Carley's writings (URL in this magazine's URL's section). The two organic acid technology antifreezes approved by GM are Texaco/Havoline Dex-Cool and Prestone Long Life 5/100.
From the car company's point of view, organic acid corrosion inhibitors
are great way to protect against warranty problems caused by customer neglect.
Most warranties are over by 5 years or 150,000 miles. Once your car is
out of warranty and you are responsible for its upkeep, even if your car
came with extended life antifreeze there's no reason you can't change the
antifreeze more often. That way, if conditions are less than perfect, you're
improving your cooling system's chances. Texaco/Havoline Dex-Cool was selling
for $6.99 a gallon at my local Discount Auto Parts store -- the same price
as conventional Prestone antifreeze.
So what would constitute a very good reason? One would be a radiator replacement with a substantially different radiator type. For instance, if the original was plastic and you put in an aluminum radiator, you'd need to totally reevaluate your choice of coolant, as this is something the car company's engineers did not design. Likewise, if the original was lead soldered copper and you're replacing with plastic. The list goes on.
Another good reason would be a known design defect involving a specific antifreeze. Certainly if the manufacturer later changed their antifreeze recommendation for a specific model, you should follow the new recommendation. And in certain circumstances where experts believe that the manufacturer was wrong, and your car is now out of warranty, you may decide to take the risk of going against the manufacturer's recommendations.
Never mix antifreezes. At best this would eliminate the long life of long life antifreezes, at worst it could cause a new corrosion problem worse than either of the antifreezes by itself. When you switch antifreeze types, you must totally drain the old antifreeze.
The environmental laws change everything. What was an easy 20 minute procedure is now a day-long affair, complete with risks of injury, car damage, and legal difficulties. For that reason I've split this article in two sections:
Before starting your coolant change, make sure you read this whole article and note the extreme hassles, damage risks, legal risks, and personal injury risks in draining a cooling system in an environmentally responsible way. Check with your city or county as to the lawful coolant disposal procedures. Sometimes those procedures are costly enough that you're better off having a shop do your coolant change.
After draining the reservoir, clean it by running a garden hose into it to remove dirt.
It seems like everyone has their own technique for draining the cooling system. Here are a few:
Be sure to let the engine cool completely each time, or you'll be burned
severely when you open the radiator cap and the radiator petcock.
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As a practical matter, you'd want to watch the thermostat and shut down the engine when the temperature begins to head for the red. Better still, have one person watch the petcock and one watch the temperature gauge, and shut down when the draining stops, or when the engine begins to head for the red -- whichever comes first. If the drainage was not complete, you'll need to use the dilution techniques discussed previously.
To increase your chances of a total drain, you might want to disconnect
the lower radiator hose. This allows coolant to drain very quickly, hopefully
long before engine temperature becomes a problem. When removing the lower
hose, try not to pry it off with a screwdriver, as that could damage the
fitting on the radiator. If it won't twist off or pull off, perhaps you
shouldn't remove this hose, unless you want to carefully cut it off with
a knife, and then purchase a new lower hose.
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One problem is that some coolant will spill when the thermostat is removed. Unless that spilled coolant is caught in a pan, it's an environmental problem, a risk to pets and small children, and may be illegal.
One possibility is to start with a normal running quick empty, let the
engine get cold, then remove the thermostat and do the second quick empty.
The second quick empty occurs immediately instead of waiting for the engine
to warm up. This lessens the risk of consequential damage to the water
pump when it operates without liquid, and lessens the likelihood of overheat.
To reduce it more, you might consider simply draining the radiator, closing
the petcock, and running until hot (at which time much of the engine's
coolant will have moved to the radiator. Because the thermostat is amongst
the highest points of the cooling system, there's a good chance that it
can be removed without significant spillage.
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But drain plug locations are specific to specific car makes and models,
and they're usually very difficult to get to. If you strip, shear or break
an engine drain plug, you're in a heap of trouble, son. And you should
really replace the washers on those drain plugs -- and those parts might
not be so easy to get. Before attempting this, be sure to obtain the manufacturer's
documentation on coolant draining
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One way to flush the cooling system is to run it with the heater running full blast, the radiator petcock open and spilling on the ground (there's no more antifreeze left, remember), and a garden hose pouring in the radiator. Such a method would take a long time to do a good flush. A much more efficient flush method is to buy a flush kit. My local Discount Auto Parts store sells a Zerex flush kit for about $4.00.
The flush kit comes with the following parts:
The other way is to use a flush kit. The preceding section discussed its installation. To flush using a flush kit, do the following on a car with a cold engine:
Also, the deflector is too short to move the spilled water away from
the car. If you use the deflector, you might want to tape a short length
of hose to it in order to move the spillage entirely away from the engine
compartment and car. Do not let the hose get anywhere near the fan, fanbelts,
or other moving parts, or the result could be severe damage or injury.
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If you connect the back flow connector in the wrong direction, or if the back flow connector malfunctions, or if you forget to remove the radiator cap, it is possible for the car's coolant to "back up" into the hose and into the water supply. This is an extreme sanitary breach, and if there are significant toxins in the cooling system (flushing solutions and antifreeze are both very toxic), people could be poisoned. Be VERY careful! |
Run the car until the fluid coming out the radiator has been clear for five minutes. At that point your cooling system can be considered flushed and clean.
Look up in your owners manual the amount of antifreeze (not coolant, but the amount of antifreeze necessary to fill the cooling system with 50/50 coolant (or whatever mixture you need to give freeze protection for your coldest days). If your owners manual lists only the cooling system's fluid capacity, divide that amount by 2 for the amount of antifreeze to make a 50/50 mixture. If, in order to protect against freezing in extremely cold weather, you need a 60/40 mixture (60% antifreeze), multiply the cooling system fluid capacity by 0.6.
Put that amount of pure antifreeze in your radiator. Then top off with distilled water. Make sure you add enough to bleed all air from the system. You should see some coolant come out the bleeder valves and/or flush T.
The reason you don't simply add 50/50 is that the engine contains 100% water, so you could never reach 50/50 by adding 50/50. Similar logic applies for any mixture percentage.
Run the car for several minutes, revving the motor every once in a while. Shut down instantly if the temperature starts heading for redline. Otherwise, let it run for 15 minutes and then shut down. Open the hood, and fill the reservoir to the "full, hot" mark with the proper mixture of coolant. Let the engine cool. Then open the radiator cap, and if the coolant isn't up to the top, top it off with the proper coolant mixture. Repeat until the cool engine doesn't require a top off.
Then, for the next few mornings, remove the radiator cap and verify that the coolant is up to the top, and if it isn't, top it off with the proper coolant mixture. Likewise, if the reservoir coolant level is below the "full, cold" level, top off the reservoir with the proper mixture.
There are two easy methods for coolant maintenance. One's not as thorough as the traditional methods, and one is expensive and might not be as thorough. But they both lower the risks of damage, injury, environmental harm and legal liability to acceptable levels. When viewing the deficiencies of these methods, keep in mind that the traditional alternatives might be even less attractive. The two easy methods are:
Start with the engine cold, and open radiator cap and then the radiator petcock and drain the radiator into a pan for disposal at the disposal facility. Also, find a way to drain the reservoir into that same disposal pan. Add a gallon of water to the radiator with a garden hose, and catch what comes out the petcock in the pan That should remove most of the remaining ounces of coolant.
Unless you're extremely environmentally responsible, you can then rinse the radiator and reservoir with a garden hose. After all, probably there are only a few drops of coolant left in the radiator, and you're diluting that coolant 100 to 1, so risk to animals and the environment is minimal. Once again, allow the radiator to drain completely, and then close the petcock. Now fill the radiator with the proper antifreeze/water combination for your climate, squeezing the hoses to try to free air bubbles.
If all went well you didn't introduce air pockets into your cooling system. But sometimes air pockets happen. Too much air can cause overheats, either through a low coolant condition, or by an air bubble surrounding the thermostat's temperature sensor.
Fill the reservoir to the "full, cool" line with the proper mixture for your climate. Place a closed bottle of that mixture in your trunk for use while testing. Now start the engine and drive it around the block a few times, keeping a VERY careful eye on the temperature gauge. If it starts to move toward the redline, shut it down immediately. Otherwise, after about 10 minutes pull back into your driveway. Either way, with the engine hot, top off the reservoir to the "fill hot" line with the proper mixture. When the car is cold again, note the reservoir level. If it's below the "full, cool" level, repeat the instructions in this paragraph.
Every day for a week, when you get up in the morning, before starting the car open the cold radiator and top off with the proper coolant mixture if necessary, and top off the reservoir to the "full, cool" line. This is replacement of air that got burped out during yesterday's driving. During the first week watch the temperature gauge very carefully. If you have no gauge (only an idiot lite), try not to go on long drives for the first week, and check the reservoir level every time you come out to the car.
For even better accuracy, before refilling with coolant, measure the coolant mixture with a hydrometer (assuming you've always used ethylene glycol), and when calculating the replacement mixture, make sure to compensate for any excess in the existing mixture.
This method takes maybe 15 minutes (not counting around the block testing or the trip to the licensed disposal facility), it's performed almost entirely on a cold engine, it's cheap (typically a gallon or 1.5 gallons of antifreeze), it's environmentally sound because it's trivially easy to catch all the coolant.
Each time you perform this procedure you replace roughly half the coolant, and as a simplification you can assume you're removing 1/2 of the coolant's disolved impurities. If you do this procedure twice a year (that's about $20.00 and a half hour of your time plus time spent testing and at the disposal facility), you've replaced 75% of your coolant every year, and every 2 years you've replaced 93.75% of your coolant. This isn't as good doing a 100% replacement and backflush every 2 years, but if you continually refill the radiator every 6 months it's probably good enough to keep your cooling system healthy for a very long time. And remember, without knowing exactly what an auto shop does, it's very possible that this procedure is actually more thorough than what the shop does.
A huge advantage of frequent radiator drains is that you control the
water being used. By using only distilled water, you cut way down on the
likelihood of calcium-caused deposits. Even if your system started with
tap water, within 4 changes you've replaced 93.75% of the old tap water
with distilled water.
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Be sure the professional uses the correct antifreeze for the car. Some
shops don't take the time to look up recommendations. And ask whether the
shop is using recycled antifreeze. Recycled antifreeze is made from old
antifreeze and contaminants -- many from cars much dirtier than yours.
The quality of recycled antifreeze is dependent on the ability of the recycling
machine to filter out whatever bizarre contaminants were present in the
raw material, and upon the corrosion inhibitor which the shop adds. With
new antifreeze priced at $6.99 a gallon (add a couple bucks for the shop's
markup), recycled antifreeze might not be worth it.
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My computing life is uneventful these days. I write books, just like I always have, except now I have superior book writing software (LyX). I use outlines just like I always have, except now my outline processor (VimOutliner) is keystroke friendly and extremely fast. I write web pages just like I always have, using the Linux version of the software I've always used (Netscape Composer). I do weekly and monthly backups just like always, but now I can script the whole thing (tar and cdrecord) instead of enduring the irritation of point and click.
Life after Windows? It's business as usual.
Do you long for the maintainability of the Bel Air, the Dart, or the original Beetle? Then you just might like Linux. Like the cars of yesteryear that could be repaired with little more than an adjustable wrench, the Linux computer can be repaired with a text editor and a few basic built-in diagnostic tools. No regedit or DLL evaluation necessary.
But maybe you're more the Lincoln Town Car type of guy. Then you just might like Linux. I'm writing this magazine on a dual Celeron 450 with 512 Meg of RAM and 80 Gig of 7200 RPM disk, using Mandrake Linux. I have LyX book authoring software, which is definitely the Cadillac of the industry. For daily drives through web authoring land I use Netscape Composer. I have email clients, news clients, irc clients, and everything else I'd ever need for a full featured desktop computer.
Which is boring to an eight barrel carburetor Pontiac Trans Am type of guy. If you like to soup up your Trans Am, you just might like Linux. With Linux, you can download and install almost any conceivable type of software. And if you can't download it, you can code it yourself. And when it comes to performance, Linux is king. As installed. But if you want some extra performance, you can tweak Linux for plenty of extra horsepower.
If you're an environmentalist who has an electric or hybrid car, you just might like Linux. Linux doesn't use or support the Microsoft Monopoly. The Microsoft Monopoly limits everyone's choice and depletes the e-zone layer.
Perhaps you're the price sensitive type, driving a Kia Rio or Toyota Echo. You just might like Linux. A full featured Linux box set with bundled customer service costs between $29.00 and $89.00. A CheapBytes.Com CD set can cost less than $15.00, delivered. Or, if you have broadband connectivity, you can download your favorite Linux distribution free of charge. Better yet, when you use Linux, most of your software is free. The LyX professional book authoring software is free. The Gimp professional graphic editor is free. The OpenOffice office suite is free. The server software most common to the Internet is free. And don't forget that because Linux is more efficient, you spend less on hardware for a given performance level.
Price is important, but you might be the type who searches Consumer Reports for the most reliable car. If so, you just might like Linux. Linux seldom freezes, and when it does you can usually unfreeze it by finding and killing the rogue process with the top command. Unlike some of its competitors, installing applications usually does not affect the underlying operating systems, and "de-installing" a Linux application usually removes all trace. While Linux's competitors place their graphical user interface in the kernel, meaning a graphics crash can bring down the whole system, Linux places the graphics outside the kernel, where it can easily be stopped and started independent of the operating system.
Are you the type who pays cash for your car so you own it instead of the bank or the leasing outfit? Then you just might like Linux. With Linux, you own your software and data. You can legally modify your software any way you like. Because most Linux data is text, you can use editors and scripting languages to access and modify your data. You can switch to another distribution or operating system any time you want. Unbelieveably, it is perfectly legal with most Linux distributions to install your Linux distribution on multiple computers, whether or not those computers belong to you. Contrast this with modern commercial operating systems, which prohibit reverse engineering, force you to register your operating system, and cease working if your hardware changes substantially. Rumors abound that many commercial software vendors are considering moving to a software rental scheme. If ownership of your operating system, your computer, and your data itself is important to you, Linux is your operating system.
Are you one of the few skilled enough to build your own car from a kit? Then you just might like Linux. The Linux From Scratch (URL in URL's section) website gives complete instructions on how to build a Linux system with source code you download and compile yourself. It's a lot of work, but once you've completed this project, you have exactly the system you want, with no extraneous features or geegaws. And you intimately know every software component in your system.
Linux comes in several models (distributions in Linux-speak). Distributions include market leader Red Hat, easy desktopping Mandrake, Ultra-free and maintainable Debian, trivially simple Lycoris, and no-frills Slackware. URL's for these distributions are in the URLs section of this magazine. Additionally, there are tens of other widely used distributions. Each distribution focuses on a specific needs scenario, but like the Chevy Bel Airs of the 60's, Linux is so easy to work on that you can add any functionality to any distribution.
But Linux isn't for everybody. If you're the type who drives to the closest dealership, relies on the salesman for a quick features per dollar comparison, and buys a car, you probably won't like Linux. Linux requires a little more planning.
If you suspect your current computing experience isn't the best it can be, do yourself a favor and investigate Linux. You just might like it.
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