The overheat troubleshooting strategy I’d like to recommend involves the Universal Troubleshooting Process, which is listed below to refresh your memory:

1. Get the Attitude
2. Make a Damage Control Plan
3. Formulate a Symptom Description
4. Reproduce the Symptom
5. Do the General Maintenance
6. Narrow it Down
7. Replace or Repair the Defective Part(s)
8. Test
9. Take Pride
10. Prevent Future Occurrence

The remainder of this article describes my suggestion on how to put the Universal Troubleshooting Process to work in diagnosing an overheat.

Get the Attitude

Overheats and the threat of broken head gaskets or broken/warped heads can tax anyone’s state of mind. Remember that no matter how bad it is, you’ll probably get out of it for $2000.00 or less. Maybe a lot less, like less than $100.00 if it’s a bad hose. And after this you’ll never let the car overheat again. Accept what comes your way, and vow simply to diagnose the problem in a systematic and accurate way.

Make a Damage Control Plan

Safety, safety, safety. Cars can burn you — especially overheated cars. Understand that you never remove the radiator cap while the engine is hot. Open only after it’s cooled to the point where you can comfortably leave your hand on the radiator for 5 seconds. Even then, be sure to cover the cap with a towel before removing the cap, to prevent spraying. Always wear safety glasses when working on a car, make sure long hair is pinned up tight to prevent it getting caught in the machinery. For the same reason, remove jewelry and even rings.Make sure to stay well away from an open carburetor, or even the air intake, when running the car. Backfires can cause third degree burns. Take care not to short the battery or cause any sort of spark, as batteries can explode, throwing acid at anyone near. Never work under a jacked up car unless it’s been blocked up very securely, and even then keep in mind that the car could be hit by a careless driver or dislodged by an earthquake or extremely strong wind. Wear strong shoes to prevent injury if you should drop a heavy part on your foot.

Resolve to not let the temperature go into the red during testing and repair. Make sure to shut down the engine long before it gets to the red, remembering the engine will heat up more after shutting down.

For further thoughts on safety, see the Troubleshooters.Com Overheating Guide. The time to think of safety is BEFORE beginning your repair.

Formulate a Symptom Description

Does it overheat? Under what conditions? Is it more likely to happen in stop and go traffic, or at a steady 65mph? Is there evidence of coolant loss before the overheat? Do you see dripping coolant anywhere? Billowing steam out the exhaust? Yellow gunk on the oil cap? Continuous bubbles in the radiator? Does the fan ever spin? When?When did you first notice the symptom? What else happened at that time? Were later occurrences different than the first (an initial low-coolant caused overheat could crack the gasket, after which the cracked gasket could cause overheats even at full coolant). Has the symptom been changing with time? What repairs and maintenance have been done on the vehicle?

Reproduce the Symptom

NEVER DELIBERATELY CAUSE AN OVERHEAT!!! Instead, demonstrate that there is no reasonable “stopping point” on the temperature. Well maintained vehicles always stay well to the left of the red on steady, flat drives. A temperature gauge that goes 2/3 toward the red is very good evidence of a problem. Be sure to shut it down when it reaches that 2/3 point to avoid it actually going into the red.Subsymptoms such as steam out the exhaust, yellow gunk on the oil cap, dripping coolant, should also be verified at this time.

Do the General Maintenance

General maintenance consists of things that should be done regardless of problem, and easy and obvious steps. Make the following observations while the vehicle is not hot or running. Note that these steps combined should take a few minutes, but they can save costly and embarrassing mis-diagnosis:

• Coolant full?
• Coolant mixture OK? Hydrometer reading ok, color ok, no oil in coolant?
• Radiator deposits? Drain enough coolant to see some of the tube ends.
• Radiator cap OK (no cracks and swelling)
• Radiator has clean air flow path? Bugs? Leaves? Clogged air conditioning coils in front of it?
• Radiator dented or otherwise obviously damaged?
• Hoses OK? Feel them.
• Coolant in oil? Yellow gunk on oil filler cap?
• Water pump turns easily? Without excessive shaft play? Any signs of leakage?
• Belts OK, with reasonable tension?
• Evidence of freeze plug leaks?
• Head gasket bolts appear loose?

Now some observations with the engine running:

• Fan(s) run when hot?
• Thermostat work? (detect increased pressure by squeezing hose, or observe coolant flow in a radiator drained of a few inches of coolant)
• Heater work? Heater hoses hot?
• Radiator flow? View flow after draining a few inches of coolant. More rigorous tests require removal of the radiator.
• Bubbles? Look for bubbles or foam in the coolant in the radiator. If so, there might be a head gasket problem. The block tester or smog sniffer will tell.
• Steam from exhaust? If so, suspect head gasket problem.

Next, do the two chicken and egg tests:

• Pressure test OK?
• Block tester or smog sniffer reveal combustion gasses in coolant?

I’m well aware that the combustion gas test has a significant cost attached to it, but I have still included it in General Maintenance. The cost of misdiagnosing a broken head gasket is so severe that I believe it warrants the combustion gas test in all but the most obvious cases. Even in cases where a definitive cause is found, such as a broken fan belt, remember that the overheat could have consequently broken the head gasket. Obviously, if steam out the exhaust or coolant in the oil reveals a broken head gasket, you know you have a broken head gasket without doing the combustion gas test.The few minutes and dollars spent on these tests greatly increase the chance of an accurate diagnosis and estimate. Once again, remember that overheats are likely to cause consequential damage, some of which in and of themselves can cause overheats. It’s therefore common for an overheat to be found to have multiple causes.

Then there’s a modification. I cannot recommend this, as I don’t have enough information on it. But the possibilities sound intriguing. One Troubleshooters.Com visitor, a diesel technician with an ASE certification, says that he often drills a 1/8″ hole in the thermostat. The hole is too small to affect the temperature regulation, but it’s big enough to bleed out any gas accumulated at the thermostat. Such gas, whether it comes from combustion gasses or other sources (sucking back on a dry reservoir, for instance), could shield the temperature sensing part of the thermostat from the coolant temperature, thus making the thermostat “think” that the engine is cool, so the thermostat remains closed. Overheat city! The little hole bleeds off air before the engine overheats. The same T.C visitor told me in the last couple years he’s seen several thermostats, especially for foreign cars, with the hole already there. Hmmmm!

Narrow it Down

If the General Maintenance was done properly, there’s probably little you need to do in narrowing it down. Resolve any uncertainties with tests designed to narrow the scope of the problem, always keeping in mind that overheats often have multiple causes, especially in the case of head gasket problems.Does it overheat more in stop and go traffic, or cruising at 65mph? The former implicates the fan or shroud, the latter tends to rule out the fan and shroud.

Advice to the Mechanic

Inform the customer of all defective or semi-defective equipment you’ve found. Explain that it’s his choice, but fixing a head gasket and leaving the partially clogged radiator could result in another busted head gasket a week later. Explain that replacing the radiator without replacing the head gasket could result in another overheat, and maybe this one will bend the heads. Explain that driving with a broken head gasket risks a broken starter and flywheel if coolant gets in the cylinders.

Advice to the Customer

Don’t try to get off cheap in cooling system repairs. Overheats cause major consequential damage, such as broken head gaskets and even broken heads. Broken head gaskets in turn can cause broken starters and flywheels. Replacing a flywheel on a transverse engine is *very* expensive.First ascertain the condition of the head gasket. If you’re driving a cheap car, you may wish to junk it or sell it cheap upon hearing of a head gasket problem, especially if accompanied by a bad radiator. However, remember that all cars need repairs, and the car you replace it with might also need expensive repairs. So if it’s a good, reliable car in reasonable condition, it’s often best to bite the bullet and do the repair, even to the tune of $2000.00.

Once you’ve committed to making the repair, replace *all* bad and semi-bad components. If the water pump leaks or has excessive play in the bearings, replace it even if it might not have been the primary root cause. If the radiator is partially clogged, replace it. You don’t want that radiator clog to rear its ugly head on a 3000 foot climb.

I consider a finding of clogged radiator to be an opportunity to get a heavy duty radiator. I spare no expense on radiators. A high capacity radiator can compensate for a host of other problems. When my Dodge Coronet radiator needed replacement, I had Harry at Valley Radiator build me a 17×25 4 row monster. It cost me $400.00, but let me tell you, when I drove it across the country in one of the worst heat waves ever, I was darned glad I spent the money. If you don’t have a radiator shop you trust enough to custom build you a thyroidal radiator, or if you have a recent car that can’t take a custom radiator, ask for the stock radiator that comes with the car’s “towing package”. Such a radiator is designed to dissipate the heat generated while towing a trailer up a 3000 foot climb. The extra $100 or so will be greatly appreciated as the years go on.

Sometimes you have the option of repairing the radiator. If you already have a heavy duty radiator, and there’s a real opportunity to restore it to like-new condition, maybe you’ll choose to repair the radiator. But you would still have deposits and diminished capacity after repairing the radiator, I’d personally choose to buy a new radiator instead of attempting the repair. A top functioning radiator is your best defense against long steep climbs or long drives in hundred degree weather.

Replace or Repair the Defective Part(s)

Once mechanic and customer have reached a decision on the strategy of the repair, the parts are replaced and the old parts are given to the customer if requested. As a customer, I personally always request the old parts.

Test

Owner Testing

The mechanic himself should have driven the car long enough to see it stabilize at a running temperature. If it doesn’t stabilize, the repair is not complete.

Mechanic Testing

First, drive under normal conditions to verify that the temperature stabilizes at a reasonable figure. If it does, this takes guts, but I recommend a trip over a peak like the Grapevine (but no air conditioning please, cars aren’t designed to take that kind of abuse). If the temperature doesn’t stabilize, shut it down long before the temperature gauge redlines. When it cools, fill the coolant, turn around and limp home. Consult the mechanic.

Take Pride

The car no longer overheats. You can drive it over the Grapevine (or whatever passes for the Grapevine in your area). Take a moment to reflect on the fact that there was no voodoo or magic, just a root cause (possibly with consequential damage) that the mechanic and customer found and vanquished. Rejoice in the fact that you’ll now pay regular attention to your temperature gauge, discover your car’s baseline behavior, and take quick corrective steps when your car deviates from that baseline behavior. No more destructive overheats for you.

Prevent Future Occurrence

First and foremost, resolve to glance at the temperature gauge two or more times per hour. Get to know the baseline behavior of your cooling system. Upon detecting a deviation, get it taken care of. A new water pump is what, $200 installed? A new heavy duty radiator is maybe $350 installed. New hoses are about $100. Same with the belts. All of these are a drop in the bucket compared to the head gasket replacement you’ll need if your car overheats. Your temperature gauge is a very sensitive test for cooling system malfunction.Some cars don’t have a temperature gauge, instead relying on an idiot light which flashes when the temperature becomes critical. In my opinion, that light might as well have the words, “ha ha, you just broke your head gasket” written on it. At that point you can’t even safely drive it to the mechanic. My 82 Buick was just such a car. After replacing its head gasket and starter ($1150 back in 1987), I spent another $125 to have a temperature gauge installed. That gauge was probably what saved me from a second blown head gasket a couple years later.

Resolve to check your coolant level at least once a week. Get to know its level both cold and hot. Top off as necessary. Personally, I’d recommend mixing antifreeze with distilled water. That cuts down on deposits, and unless your car is using enough coolant to indicate a problem, one 69 cent bottle of distilled water will last you a couple years. If you need to top off your coolant frequently, it may be time to check your cooling system, especially checking for combustion gasses in the coolant. This is especially true if you experience unexplained coolant losses on long trips.

Resolve to treat long steep climbs and long drives with respect. Always confirm proper coolant level before beginning the trip. If you have *any* question at all about your cooling system, stop and top off the reservoir, and then wait 25 minutes for cool down and “suck back”, before beginning a long steep climb. View your temperature gauge at least every minute during a steep climb. If the temperature gets uncomfortably close to the red, pull over, run it for a minute at 1200 rpm in neutral or park, then shut it down til it cools down. Once it’s stopped boiling and sputtering, top off the reservoir with coolant so that the cooling radiator will have coolant to “suck back”. Continue adding as cooling continues to best facilitate a full cooling system.

Don’t be macho about running your air conditioning while climbing. If the temperature varies significantly from baseline, turn off the air conditioner and open the windows.

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