1994 Jeep Grand Cherokee.

It runs perfectly and engine temp is fine when I'm driving. Problem is if I leave it idling for a long period of time, or sit in stop and go traffic, it starts to heat up. It gets over the 3/4 mark on the engine temp gauge.

The only actual 'problem' with this that I can tell is that the a/c isn't very cold at this point. It gets close to, but never goes into the red.

Is this bad for the car? Is there anything I can do about it? Or is this just something that will happen to an old car sitting in 115 degree heat?

 

Water pump or thermostat problem?

 

Well the a/c cuts out, so it definitely is getting hot. Water pump would cause this to happen at low speeds?

 

If it's got a clutch fan that can affect it aswell. Sometimes when the clutch starts to go, the fan doesn't spin as fast as it needs to at idle..

When thermostats fail they won't let the car cool down when going at speed. And some of them now days fail in the open possition anyway.

If the water pump isn't moving enough water it certainly could be a problem. Mabee a coroded or busted impellar.
The radiator could be blocked inside or outside. and be preventing water flow, or air flow.

My old 429 powered truck didn't do so well here in az summers till i put electrif fans on it. I just couldn't move enough air with the old belt driven fan/shround combo, but most domestic cars from the last 20 years or so have been tested in heatboxes here in the sonora desert, so it shouldn't really happen to a 94.

 

It could be that the fan isn't switching on when you're idling.

 

Does the radiator fan turn on when the engine reaches temperature? If no, check the radiator fan switch.

 

Typical american cars, they get crazy heat soak at idle causing the A/C to blow


Beet, you may want to consider adding a better fan or/also putting it on a switch (that is what we do with our old hot rods.


But, there are many aftermarket fans out there that are a lot better then factory that will definately cool you down.

 

Not sure on the specfics of your Jeep. But from my experience with my 94 Explorer.....

If it's a mec. fan that uses a fan clutch, the clutch may be bad.(on an explorer this is common, & there will be cracks in the fan around the hub)
The coolant temp sensor may be bad
TS may be bad
air trapped in radiator
Bad radiator
I had the same problems, & had to replace all of that. It's ok now.

 

I'd check radiator fan and/or switch.

Drain/flush/refill the cooling system to ensure that the radiator is flowing properly.

If the thermostat is original, replace it...

Check coolant temperature sensor.

 

How do you check the coolant temp sensor?

 

Find where it's located. Unplug the connector & ground it. The temp gauge in the car should not move when you turn the ignition to run.

 

On the S-Series Saturn's at least, the problem is quite common...the tip would crack as the morons at GM thought plastic was OK, so the updated part is now a metal tip. If in doubt, just replace it...it's not that expensive...but check the radiator fan switch, and flush/fill the cooling system first...(and replace radiator cap)

 

There's only a fan switch if it's an electric fan.

 

Awesome, thanks for the help guys.