Another Cherokee Cooling Issue!!

2000 Cherokee 4.0 liter engine. Had radiator leek. Installed new radiator and thermostat. Was fine for about 1500 miles then all of a sudden one day the coolant starts backing up into the overflow bottle. Coolant is not hot. Just seems to be building up pressure somewhere and forcing coolant into overflow. Engine itself gets very hot. No radiator fluid in oil. Then installed new water pump figuring coolant wasnt circulating. Wrong!!! Still forcing coolant into the overflow. WTF is going on? Going to try running without thermostat see if thats the problem. Any other help would be greatly appreciated.

Nevermind. Is more than likely a blown head gasket and/or warped head. Is there any way to tell without going to a machine shop it the head is warped? Anyone want to buy a Jeep?

It's possible you have a head/head gasket issue, but I'd definitely try running it without the thermostat before anything else.

If you have a cracked head or bad head gasket, there can be numerous symptoms, anywhere from coolant in oil, oil in coolant, coolant leaks from engine block/head, exhaust leaks, etc.

There's another thread here, with references about the 0331 head used in 99 and 2000....check that one out for more, but definitely run it without the thermostat in.

I did run it without the thermostat and it seemed to make the problem worse. Talked to a guy i know who builds 4.0 engines and he said more than likely head gasket. Is exhaust leaking into cooling system somehow i.e cracked head, head gasket etc. So cylinder head is coming off today. But will look for that thread. Thanks.

Here it is, if you didn't find it:

http://www.automotiveforums.com/vbulletin/showthread.php?t=967126&highlight=0331

I found it. Removed head and took it to the machine shop. Found very small crack and the head is warped. Guy at the machine shop says everyone who has issues with the 0331 casting heads is full of crap. He must be in cahoots with the manufacturer. lol This is why i became my own mechanic. If i had taken the whole vehicle to a mechanic he would have charged me hundreds of dollars to replace a bunch of parts and still probably wouldnt admit that the cylinder head was bad. then when i insisted he would have charged me hundreds more to pull the cylinder head and actually fix the damn problem. Thank god for automotive forums.com

Right on....about both getting it fixed and the mechanic being full of it. There's too much about the 0331 head cracking for it to be a limited issue....getting a new head from a pre-99 from a junkyard?

Yes. Will be headed to the pull and pay junkyard sometime this weekend.

Right on...let us know how the replacement goes.