[SimonTuffGuy]

Took the Jeep out for a 30 mile ride on the highway last night... About 3/4 of the way there, I noticed that the temp gauge was a bit higher than normal... I'd say like 230-240 area (just right below the red).

Parked it last night and went out this morning to a small puddle of coolant under the Jeep. Added a bit and then started the Jeep. Let it run for a few minutes and realized it that it was leaking more. Crawled up under and saw that it was leaking from where the pump comes off the engine, ran down the hose and then dripped to the ground.

Stopped by the local garage and the owner (also a YJ owner) said that it was a sign the water pump was failing. Said to leave it, he'd check it out and replace it.

Got it back this afternoon. A new pump was installed, I told him to replace the serp. belt because mine was cracked.

Picked it up and drove home. The gauge went right back to where it was before, right below the red line area. Got it home and parked it, then called the shop to see what he thought. He said possibly needed a new thermostat too, but he didn't have 1 in stock.

So, I grabbed the Hayne's manual. In the cooling/heating section, it says if the engine is running hot, check the upper radiator hose. If that hose isn't hot, the tstat is probably stuck close. Mine was hot. The engine warmed up quickly, had blazing hot heat, etc. Soo... I'm at a loss here.

In the troubleshooting section, it says it could be a bunch of things... Insuffient coolant (it's filled to the top), drivebelt defective (just replaced), core blocked (possibly? He didn't say about draining it), faulty tstat, fan not functioning (It's blowing, so... I'm guessing it's ok?), timing incorrect, defective water pump, rad cap not maintaining proper pressure...

Anyone have suggestions? Would replacing the tstat be the easiest thing to start with to see if that resolves the issue? Any help is getting this fixed would be appreciated.

[pain]

I'd check to make sure you don't have an air pocket some were first. Just start it, take the cap off and wait for it to warm up and see if any bubles work their way out, be carefull not to let it over flow or burn your' self. Then if it still does it I'd change the thermostat.

[Brandon_YJ]

Your Thermostat could only be opening partially. So Haynes *kinda* mislead you there.
Plenty of things can cause an engine to run how: clogged up radiator, fan/clutch failing, collapsed radiator hose, A/F mixture too lean....

[ayerightaye]

Had a similar problam that outlasted 2 radiator replacements and 2 themostat changes. Everything was flowing and my fan was blowing but I kept runnung hot, usually around 240 or so and would hear it boiling when I parked. Turned out my fan clutch was not working properly. The clutch contols the speed of the fan and I couldnt imagine how slow mine was moving until I put in the new one. Now I run cool <180 in traffic. Cost $35 bucks aqnd about an hour for the easy fix.

[kharmajavah]

Yep...my vote is fan clutch, especially if it happens in town, at stop lights/in traffic. Usually a thermostat replacement is pretty standard with a water pump replacement, so I'd to that, too, just to cover your bases. Thermostat replacements are easier than changing your oil.

[SimonTuffGuy]

I'm guessing that with the shop doing the fix (and him being a YJ owner), he would've got the air out of it. Possible that he didn't... But, I think maybe I'll swap out the tstat anyways (could be a quick, cheap fix if that IS the problem).

The fan SEEMS to be running the same as always. Possible that it's not, so... I guess maybe that's something to consider too.

[SimonTuffGuy]

Is the fan clutch outlined anywhere in the Hayne's manual? I can't seem to find anything about it.

[SimonTuffGuy]

Nevermind... Found it. :-p

[rustywrangler]

I'm gonna vote for the fan clutch as well. The fan clutch can go bad and cause the water pump to have issues eventually causing it to fail and leak.

[havasu]

Just a question...was your radiator cap replaced as well? If it's old, it won't hold the necessary pressure.

[tato1111]

If u have been threw mud lately the back of the radiator may be clogged, that happened to me once but idk.

[MLJeeper]

Good way to check your fan clutch (not 100% though) is to grab your fan blades and see if there is any play in the fan clutch. There should not be any forward/backward movement. This can definitely cause your problem. If youve replaced the pump, stat and the fan clutch checks out, remove the radiator and have it rodded or replaced. Leaking head gasket would be an issue too, you can check for water in the oil and look at the plugs for an indication of this problem.

[rustywrangler]

Originally Posted by MLJeeper

Good way to check your fan clutch (not 100% though) is to grab your fan blades and see if there is any play in the fan clutch. There should not be any forward/backward movement. This can definitely cause your problem. If youve replaced the pump, stat and the fan clutch checks out, remove the radiator and have it rodded or replaced. Leaking head gasket would be an issue too, you can check for water in the oil and look at the plugs for an indication of this problem.

Only saying this because it has happened before:

DO NOT DO THIS TEST WITH THE ENGINE RUNNING!!!!!!!!!!!!!!!!

[gary92yj]

With your engine off and cold you should be able to spin your fan by hand.Then start the engine and let it get hot.you should hear when the fan clutch locks up and spins the fan.if you're running real hot and shut the engine off you should not be able to spin the fan until it cools down again.It could also be a faulty temp gauge but i doubt it if you hear boiling and had pump trouble.

[Brandon_YJ]

You have GOT to point me to the thread where this happened (if any)!!
That's like people taking Preparation-H orally.... and stuff.

Originally Posted by rustywrangler

Only saying this because it has happened before:

DO NOT DO THIS TEST WITH THE ENGINE RUNNING!!!!!!!!!!!!!!!!