Overheating problem

[basshunter]

Hello, all:

I have a 2001 Grand Cherokee, 4.0L six with air. The other day I passed a car and shortly afterwards, the temp gauge pinned at 260. I took it to a "pro" and he did a block and pressure test--they both came out good. He suggested a new radiator--got one and put it in--no change. I flushed and backflushed the heater core to eliminate any blockage that could have built up. The engine even overheated without the thermostat. The water pump seems to be OK--no leaking, grinding, etc.

Note--the transmission has almost no 2nd gear thanks to the previous owner. The only other symptom I can think of is the system is under a ton of pressure, but doesn't fill the overflow reservoir. The upper and lower radiator hoses are hot and very hard. The oil looks good--no visible signs of coolant there. There isn't any smell of antifreeze at the tailpipe, nor is there any coolant inside the passenger compartment.

I'm convinced I have a phantom in my engine.

Any help would be appreciated.

Thanks

Bob

 

[54cj3b]

http://www.jeepz.com/forum/cherokee-commander-wagoneer-liberty/29928-running-hot.html

common both in xjs and zjs

 

[donnie850]

check the vac. line going to the heater control valve (guess thats what its called?). Thats what was wrong with mine. Well that and the part was bad to begin with.

 

[SteelHeadz]

If i remember correctly, you have 2 cooling fans in your 01 GC. One is the clutch type fan mounted on the front of the water pump and the other one is the electric fan mounted directly behind the radiator. This fan is a helper fan for the cooling system, if it fails even if the clutch type is still good, it will still overheat. Check to see if you do in fact have this electric fan and verify that it's working properly.

 

[basshunter]

Thanks guys............

I only have the electric fan on this model and that frigging fan relay gave me fits last year so it was the first thing I checked (OK, maybe the second thing). It is working now.

Another thing--the heater blows cold air even when it's about to go over temp--feels like the ac is on, but no fluid inside the compartment. I thought it might be air-locked at first but can't find a good manual to show me how to burp the engine the right way--I read one place where it was done at the thermostat housing by replacing the sensor unit with a brass petcock and burping it there. I also read there's a plug on the block somewhere to do it. What would cause this to happen with no warning?

Bob

 

[donnie850]

This really sound identical to the problem i had! replace this part if you have it.. and make sure both fans work!