Overheating? Quick help please.

[UltimateG]

Hi.



I had a problem with my engine overheating today. I’m hoping someone smarter than me can tell me exactly where the problem lies.


The Jeep: 1994 XJ. All stock. Runs great, and never any history of cooling problems. I am pretty sure the coolant mix is roughly 50/50% water/EG. (But I may be mistaken about that). The radiator, water pump, and hoses are all newer, and have all been replaced within the last 7 years / 40,000 miles.

The setting: Weather has been very cold. Temps were -5 degrees Fahrenheit this morning. The Jeep has not moved in the last four days.

The situation: This morning when I started her up, everything seemed normal. A couple miles down the road, (~10 minutes) I noticed the temp gauge was getting high. It just kept climbing, and didn’t stop at 210. The needle kept going up to the red zone. Once she got close to 250, I turned off the engine.

This entire time, the heater was blowing completely cold air.

I looked under the hood, and there was a little bit of steam & water coming out from the radiator cap. Everything else looked okay.

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I let the car cool down for a few hours. Then drove it back home. Everything seemed fine. The temp gauge stayed below 210 the whole way back.

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So, where exactly in the system did the malfunction occur?

Thanks!

[maxbraketorque]

That's a pretty unusual set of conditions for overheating. If the thermostat were stuck shut, that would cause overheating, but your heater would blow hot air unless the heater core bypass valve was stuck in bypass mode.

How much water is in the radiator now?

[UltimateG]

Radiator seems full.
The bypass valve has been removed, so core is always toasty.

[Anak]

The first thing I would do is confirm the coolant level in the radiator.

The second thing I would do is test the coolant for its freeze point. (Parts store will carry a cheap test tool if you don't already have one.)

I would next get an IR temp gun (or some other way to measure temperature besides what the gauges are saying) and compare temp gun readings to instrument readings.

If all three of those things test okay I would then be looking for some sort of blockage in your hoses or thermostat or some sort of freak problem such as a water pump impeller come loose.

Thermostat is the problem you are hoping you have, and I think the most likely culprit. I think if it were stuck closed you would not get much (if any) circulation to the heater core.

[maxbraketorque]

Originally Posted by Anak

The first thing I would do is confirm the coolant level in the radiator.

The second thing I would do is test the coolant for its freeze point. (Parts store will carry a cheap test tool if you don't already have one.)

I would next get an IR temp gun (or some other way to measure temperature besides what the gauges are saying) and compare temp gun readings to instrument readings.

If all three of those things test okay I would then be looking for some sort of blockage in your hoses or thermostat or some sort of freak problem such as a water pump impeller come loose.

Thermostat is the problem you are hoping you have, and I think the most likely culprit. I think if it were stuck closed you would not get much (if any) circulation to the heater core.

If the thermostat is stuck shut, the only circulation that occurs is through the heater core (as long as the bypass valve is remove or not bypassing), so if the heater did not blow hot air and there is plenty of water in the radiator, it would seem to suggest one of the items you mentioned.

[Unclewolverine]

X2 if there is no valve there is always water circulation in the heater. With described symptoms you are either low on water or it froze.

[tech1001]

I would say the coolant was frozen , do a flush and add the antifreeze you need to stop it from freezing where you live and the temps you have .

[TheXJDrew]

Sounds like frozen coolant to me and that it somewhat thawed out after the engine warmed up. As mentioned above, a good flush and the proper coolant and mixture would be the first thing I did.

[En2 4355]

5 below on a 4 day soak?

At a minimum heater hoses and thermostat were ice bound on a poorly mixed system.

first thing is future protection. flush refill and verify frz pt.
soon. ain't like that cold snap was a one time thing

Then, if you have a pressure tester- test the cooling system.

if not, do some exploratory idle time and short drives.

see what happens.

[75SV1]

I'd replace the radiator cap. Also, I'd check the water pump. I had one in a Dodge Neon, that the impellor came off. 7 years is a coolant system Maintenace time.