tapman

My 91 has 250k on it. a few weeks ago, I had a problem with it overheating. Noticed it was running a little hotter than normal, maybe would float up to about 220, then back down to 210 where it had always been.That being said, I went on a road trip, about 100 miles away, was ok for the ride there, watching the temp. Still keeping an eye out on the temp on the way home, although not as much as I should have. got off the interstate and it shut off.Temp was pegged. Got it towed home replaced the t-stat, burped it all was well. went on another road trip about 300 miles round trip, no problems. Now it started overheating again. Radiator if fairly new, bought from a friend. Fans all work. Have not done any head gasket, or the other temp problem tests yet, but my main question is with 250k on it, is it worth doing the head gaskets, if it needs them. I know that 350 k is not unheard of on a 4.0. Thanx for your opinions tapman

XJ Stryker

Before you do any of that. Change your Coolant pump. It could be wore out. And the job is not difficult at all. Yes the Jeep still has life in it and YES it is worth it.

The fins on the pump could be worn and not circulating the coolant as well anymore. You will be surprised what a new coolant pump will do for it.

tapman

My mechanic and I were discussing whether that was a possibility or not. That was on the list of things to check before we even considered the head gasket.For all I know, it could be the original water pump. Thanx for the input.

kcenderjim

I have the same issue on my '90. Radiator, Pump, Thermo and hoses are all brand new... i am so lost on it. Thought it was just me....

winston427

You should also look into the heater control valve. My 91 was having run hot issues and I had replaced everything execpt the radiator and heater valve. If the heater valve is old and has any corrosion or deposits built up inside it can have an effect on coolant flow. I did the valve first, it's only a $20 part, and it made a small difference but did not cure the issue. I ended up swapping in a 3 row radiator last weekend to finally cure my issues. Since your radiator is fairly new, I would start with the water pump and heater valve.

kcenderjim

this is my first Jeep, im an old hot rod freak. Where is the Heater Valve?

Abovetimberline

the heater valve is located on the passengers side next to the firewall,just follow the hose off the water pump,it will be connected to it.

kcenderjim

Thanks!!!!!

brucebo

How can the heater control valve affect overheating in an otherwise functional cooling system? It just opens and closes the path to the heater core right? If it's stuck closed it's just like having the heater off. It's a parallel path with the main radiator flow. I understand turning on the heater can help cooling, but that's generally not an acceptable option when it's 90+ degrees outside. Turning on the heater when it's hot outside is generally considered an "emergency" maneuver.

-Bruce

winston427

Any part of the system that may be malfunctioning can cause issues. It is not one part that keeps the engine temp at normal operating level. It is a complete system and all parts must function properly. I understand your point of it being stuck open or closed is the same as having the heater on or off. The heater control valve on my 91 was partially blocked with corrosion buildup resulting in a 50% coolant flow reduction through the valve. While this was not the only faulty part and I recently replaced the radiator as well, I did see a difference in engine temps after changing the valve.

BuckB91XJ

I have owned my 91 XJ Sport 4.0 HO for 4 years, now. In that 4 years I have done the Heater Control valve X 2. Both times it was because the plastic POS was leaking. Thanks Chrysler engineers for such a great design...NOT!!!!!! Hey Brainiacs, how about the same design only in a STEEL version....LOL. The older Renix XJs even had a metal heater control valve. The one in my son's 87 XJ works awesome!! The good news is this, other than the heater control valve cracking/breaking and leaking all of your coolant out, it's not going to cause you any overheating problems.

Over the 4 years of owning mine I have installed the following:

1.) (New Waterpump) because the seal visibly blew out (water pouring out the weep hole. I replaced it with a OEM from Schmucks.
2. (New T-stat). I installed a 180 in place of the OEM 195. Some guys agree with this, some don't. It works great for me. Since my radiator change it sits right at 180 degrees cruising down the freeway at 75-80 mph.
3.) (New Radiator) because the left side plastic POS tank blew out on my OEM Radiator. I replaced mine with a CFS 3 core all metal radiator. Since putting in the new 3 core radiator I have had NO more cooling issues. That was 2 years ago. I believe all XJs with the 4.0 motor should have come from the factory with an all metal 3 core radiator.

tapman

Update: My jeep sat at the mechanics for almost 4 weeks til he could get to it My fault, I told him "when he could get to it". It is not my daily driver, so no real big deal. Anyway, when he did get to it, ran it for 20 minutes, and then drove it for about 15 minutes, temp never got above where it was supposed to. Laser thermometer to the t-stat housing, not above 216, just verifying gage accuracy. No anti freeze in oil, no oil in anti freeze, all is well.I drove it this weekend, even hauled a trailer. Temp stayed where it belonged. I will keep a close eye on things, but I guess I will have to wait til we have temps in the 90's again to see if there are more problems. Thanx for all your suggestions.

Ian96XJ

What did you end up doing to it? Replace water pump?

tapman

Nothing was done except that it sat at the mechanics for almost 4 weeks. They did nothing but check it and it was OK.