I have a 2000 Jeep Chreokee 6 cyl that was leaking water from the water pump. I replaced that, then the radiator failed and I replaced that and the t-stat, but I still have a overheating issue. I run the car and it goes to over 210 then jumps to 260 or so shortly after (about 5 min). Both fans are functioning. When I turn the engine off I get bubbling from the reservor. What could be my problem?????

 

Try turning the heater on full. No need to run the blower motor. Leave the rad cap off and fill as the coolant level goes down in the rad. Once the coolant begins to overflow put the cap back on and check for proper coolant level in the reservoir.

 

Sounds like the thermostat is sticking. Possibly a pressure problem. I ONLY use a good thermostat like STANT. There are so many times over the years that I put in a thermostat only to pull it out within a week ( Mine and other peoples cars and trucks). Started only using Stant stats and never had a problem with them since.

Also if your system is not holding pressure you will boil over --The reason the system is under pressure is because every 1lb of pressure exerted on the system RAISES the boiling point 3 degrees. Ever wonder why water boils in a pot at 212 but your car can run at 220 no problem.

 

Thanks I'll give this a try...

 

Did it overheat at the time of original cooling system failure? If yes then you may have a blown head gasket. Monitor/check your motor oil for white foamy-sludge on the dipstick and/or white foamy-sludge under the rad cap. If it appears in either location then it's time for closer testing/investigation. Consult a pro.

 

I have replaced this twice with Stant t-stats one @ OEM Spec 195 deg and the other @ 180 deg. I thought the first one was the issue and went to a lower temp t-stat, but still overheating. What could be the pressure issue?

 

No, the first failure was at the water pump. Then the radiator failed the next day. I checked for this issue and found no sludge on dipstick or rad cap.

 

Keeping it simple - replace the rad cap...

 

Old fan clutch? Shroud in place?

 

Is the radiator cap holding pressure?
You could also have a bad head gasket and are getting exhaust gas into the cooling system. This can cause overheating.
Did the radiator split when it failed?

 

Replaced with a new Stant rad cap. I was hoping it would have been this simple. Thanks...

 

Clutch fan is in operational condition no obvious noises from the bearing and moves freely. Shroud is in place as well.

 

Yes, replaced old rad cap with new Stant rad cap. Yes, the rad did split at the plastic end caps, right where the coils end and the plastic begins. I'm begining to think it may be a bad head gasket. Would there be another tell-tail sign this would be the case?

 

You have a 2000. From the factory, your engine came with the infamous 0331 cylinder head. This head has a casting defect between cylinders 3-4, which can lead to cracking in that exact spot.

A cracked head can give you the symptoms you describe. On the 0331, the head cracks way more often than the head gasket fails.

If this were mine, I would pull the valve cover and with a good light, perform a thorough inspection between cylinders 3-4, as many times, the crack can be seen with the naked eye.

And you really need to read this thread on the 0331 head. It is "required" reading for anybody with an 00-01 XJ.

http://www.jeepsunlimited.com/forums...d.php?t=391831

 

There is a test you can have done that will detect if you have exhaust gases in the cooling system. That would be my next step.