Why is my car overheating?

[TheWizardOfMudd]

I'm getting ready to go check it.

Low on water/coolant?

Low on oil?

Thermostat gone out?

What else could it be?

Thanks.

[GOPisEvil]

1. malfunctioning water pump...

...but that's unlikely. Hole in a radiator hose. Some other coolant leak.

[Another Bill C.]

2. Fan clutch n/t

n/t

[Th1onein]

3. Your heater core is busted.

[Ready4Change]

4. Lots of possibilities

Some more:

Old hoses binding and restricting fluid flow.
Radiator surface clogged with mud, or airflow otherwise blocked.
Brakes binding, causing engine to work harder than needed.
Out of tune, running too lean.
Failed water pump.
Waterways clogged, radiator needs internal flushing/cleaning.
Leaking radiator cap releasing pressure in system. (Likely accompanied by fluid loss.)

[radwriter0555]

5. you need a new thermostat.

it'll be FINE.

[rucky]

7. That's always the first thing to check

it's the cheapest & easiest fix, and the most likely culprit.

speaking from experience.

[jobycom]

6. Radiator cap, dirty radiator fins, obstruction

Depends on age and type of car. There are a ton of little things it could be, from oxygen sensors to EGR valves, to all kinds of little valve gadgets.

Check fluids first. If they are low, that's the problem. Refill, then test. If it begins overheating again soon, check water level again. If there is a leak, check water pump, hoses and the radiator itself. Park it one night over a piece of cardboard, you'll find where it's dripping.

Check to make sure nothing is stuck in front of the radiator, or that the radiator fins are clean. Air has to flow through them.

If fluids are fine, it could still be the water pump, a loose water pump or fan belt, a malfunctioning cooling fan (the one by the radiator) or even a faulty radiator cap that fails to keep proper pressure. These are a little easier to check than it sounds. Run your car until the temp gauge reaches what would be the normal temperature, then see if the fan comes on. Watch the belts to see if they flap around. If it's an electric fan, there could be a problem with the gadgets controlling it.

Look for other problems or patterns. If the car only overheats in traffic, for instance, or only when climbing. Notice whether the AC has a problem when the car overheats. There is a valve that regulates the AC that can malfunction and make the whole car think it is cooler than it is.

There are three basic things that can be happening, to sum it up. Either there is a malfunction with the radiator or water pump, so that it's leaking fluid or pressure. There is a malfunction with a sensor which tells the car to start cooling the water. This could be the thermostat or any number of sensors. By a Haynes manual, or take it to a shop. The third problem is that the exhaust and emmission valves could be malfunctioning, so that the exhaust gases are not leaving the engine properly, and thus heating the engine beyond what it can cool. For those, you either need a manual and some patients, or just a mechanic. They can run a scan on your engine and find a lot of that with little effort (but lots of money), but it's not nearly as much fun as busting your knuckles on rusty manifold while teaching your neighbors' kids a new vocabulary.

[TheWizardOfMudd]

11. All of you people are great

Thank you.

[kcwayne]

8. Check the simplest things first

1) coolant level
2) Broken fan belt
3) Themostat
4) water pump

If it is not 1,2,3 or 4 (in that order) then you are in the 1 percentile range for weird problems, and only then do you start with any thing else.

[sendero]

14. I would add to that list..

... the fan. While the engine is up to temp and sitting at idle, it should be turning. If the overheating tends to happen at or soon after traffic stops, that is the most likely thing. If it does it on the open road, that's not it because you don't need a fan with 40mph winds blowing on your radiator :)

[Ganja Ninja]

9. Build up of crud in the radiator ...

If you haven't had the car long and it was used it may have had a leak in the radiator they might have used some additive which can plug up the leak and the radiator too.

[fairfaxvadem]

10. Depending on it's age, may be radiator

Usually thermostat goes first, but radiators are now made, partially at least, with plastic, and develop fine cracks.

Good luck. What a hassle.

[TheWizardOfMudd]

12. MY RADIATOR WAS PRACTICALLY FREAKIN' EMPTY!!!!

I guess the next question is, where did the water go?

Into the shop it goes next week for tests.

Thanks again.

[ProfessorGAC]

13. I Have A Small Leak In Mine

It's a small leak around the hose fitting on the outlet, back to the water pump. I don't even bother worrying about it. I just keep an eye on the overflow bottle. When it's less than half-full, hot, i just top it off with 50:50 coolant.

I know where the leak is, and it's not worth putting money for something this trivial into a 10 year old car. As long as i can put the top down on a sunny day, it's all that matters.
The Professor

[sendero]

15. Fill it up ...

.. (when cool), start it up and let it run until it's hot.

Look around, you will probably see where your coolant is going :)

[bratcatinok]

16. Check for pinhole leaks

in your radiator. My car was doing the same and the dealership wanted to replace the radiator. I took it to a local non-dealership shop and they sautered (sp) the leak. Saved me quite abit of money even though the little shop couldn't guarantee the fix. As far as I know the fix is still working. (I sold the car 2 years after having this fixed.)

[CrownPrinceBandar]

17. Check for coolant in the oil..........

and vice-versa. If so, you may have cracked cylinder head. ---------> Worst case scenario.