The overheating guide. I've had a lot of car's in my day, and since one of them was a Fiero, and all of them were old, I've had more than my share of overheating problems. Since I've seen a lot of people asking about overheating problems, I've decided to try and distill down my experiences, and see if I can't help out.

Maintenance:
The absolute best way to handle overheating is to prevent it. At least once a year, check ALL of your coolant hoses. Squeeze them a bit, shake em about. Make sure they are still tightly attached, and don't have any kinks, cuts or heat spots on them. If they look even a little bit in question, replace them. It's cheap insurance. Replace the radiator cap as well. In many cases, you can get a cap that holds a little more pressure than stock, and this can help you run cooler. Every couple of years, replace your thermostat. Be sure and test it before you put it in, I've seen a few bad from the shop. You might also want to run a thermostat that opens at a cooler temperature than normal, though you need to be sure your car still hits normal operating temperature if you do this. If you live in an especially warm climate, or have a car that tends to overheat, you can ever run without a thermostat, though again, you need to be sure your car still hits normal operating temperature if you do this. Change your coolant once a year as well. Be sure and use a good quality coolant, and never use less than 10% coolant. If you live in a hot area, or subject your cooling system to a beating, Redline's Water Wetter really does do a good job.

First Aid Kit:
You should ALWAYS carry the folloing in your car if you think there is even a very small chance you could overheat: a cup of pepper, hose tape, a gallon of water, a quart of coolant, a small toolkit, fan belt (if your car uses one).

Emergency proceedures:
O.K., you've done what you could, and now you're overheating on the road. What can you do? If you're running hot, but not yet overheating, you may yet be able to get home. Open the windows, and crank up the heat, the heater core of your car is, in fact, a small radiator. Shut down EVERythING else that you can... extra lights, radio, AC and anything else that contributes even slightly to engine load. If you happen to know the portion of your RPM range than runs the lowest EGT's keep the car there, otherwise, keep the RPM's as low as you can.

If you're really heating up, pull over, and pop the hood.

If your car comes equipped with a fan belt, ensure it is attached, and working well. If it is not, replace it.

If you can see water dripping, try and see where it's coming from. If it's coming from a hose, the hose tape should take care of it. If you can easily remove the thermostat, do so to help ensure maximum cooling.

If it's a leak you can't find, wait a bit, release pressure from the cooling system, add a coulple tablespoons of pepper to the coolant, and top off with the water. In many cases the pepper will seal off your leak, and hold at least long enough to get you home.

In any event, there are a couple things you can do to help mitigate overheating. First off, if you are able to easily remove the thermostat, do so. This ensures max flow to the radiator. Some people claim cars will overheat without a thermostat... that's B.s. Tell such folks to look up "convection" and "conduction" and tell you which transfers heat better.

Secondly, if you have the know-how, short your fan switch to be sure your fan stays on 100% of the time.

Remedies:
You are now at home, or someplace where you can work on your car, and it's time to fix the problem... what to do? Well, the first thing to do is try and identify the source of the overheating. Here is a list, more or less in order, of the things to check.
1: Check the thermostat. These things have a mind of their own, and they always seem ready to go out at the worst possible time. To test a thermostate, drop it in boiling water, and watch to be sure it opens.
2: Check your fan. Short the fan switch and be sure it is operation. If it is, when your car is hot, be sure the fan actually comes on. If it does not, the temperature sensor may be bad, or possible a fan relay may be bad. When replacing your fan, you may be able to replace it with a fan that flows better than stock. If you can, it certainly won't hurt.
3: If your car overheats only with the AC on, there may be yet another fan problem. Most cars automatically turn on the fan during AC operation regardless of temperature. If your fan isn't turning on, this could be the cause of the problem.
4: Check the fan belt. Be sure it is not slipping, or broken. You may also have a problem with your fan clutch. Be sure your fan is blowing, and blowing well. Be sure it is blowing harder when the car is warm. If in doubt, replace the fan clutch.
5: Check your radiator. After driving a lot, you may get a lot of crap in the fins, and they may be bent. Straightening the fans, and cleaning the radiator can often have a dramatic effect on cooling. You might also want to run a cooling system cleaner. These can help dissolve crud in your radiator that restricts flow. You can also remove the radiator and force water through it to try and dislodge stuck particles. Finally, if you still suspect the radiator you can get it flow tested to be sure it's flowing well. If you need to replace the radiator, I'd reccomend you go with a "race" version with better cooling, or at least a larger replacement (if possible). Never hurts.
6: Check for leaks. Even a small leak can reduce pressure in the cooling system, and that reduces its effectiveness. This includes checking the radiator cap, the hoses and the radiator.
7: Check your timing. Running a car with incorrect timing can cause it to run hot. If your running a bit hot, retarding the timing a bit can help.
8: Check your compression. A poor head gasket seal can definitely lead to overheating, and a compression test is a good way to tell if you have a problem there. If you have compression numbers that seem low, one cylinder 15% or more lower than it's neighbors, or one cylinder 20% below all others, you have some sort of problem that indicates you need to pull the head.
9: Check your oil and coolant. If you see either one in the other, you have problems. Oil in the water will generally show up as a sheen on top of the radiator fluid when you open the cap. Water in the oil will show as a sort of "chocolate milkshake" looking contamination when you drain the oil.
10: Change your oil. Sounds like a little thing, but dirty oil and a clogged filter CAN make a difference.
11: Exhaust leaks. Believe it or not, an exaust leak under the hood can also make a huge difference in the running temparature of the car. Adding more heat to an already hot place is a problem, and the radiated heat of an exhaust pipe is far less than the heat content of releasing exhaust into the engine compartment. A mechanic's stethescope can help find these leaks in a hurry.
12: Proper engine compartment venting. This goes along with 10. Many engine compartments have specific areas to help vent underhood heat. Be sure these are not blocked. My Fiero not only had a vent, but a fan to help with the venting. Again, a small thing, but one which makes a difference, and can make a difference between skating along, and overheating.
13: Change your gas. Sometimes you just get a bad batch, it causes your car to pull back the timing, temps rise, and booya. You might even try running a higher grade of gas.
14: Check your vacuum lines. A clogged vacuum line, a stuck solenoid, or a leaking Tee can cause your emissions system to malfunction, and help your car run hot.
15: Last thing I can think of, check your guag and temperature sending unit. It's possible your car ISN't really overheating.

This is a living document. If you have suggestions for improvements, or additions. Please feel free to post here, IM me, or email me.

 

good post

 

most useful post ive ever read...

from me

 

very informative