Alright, alright ! I know that this problem has been beat to death, but i've been searching for an answer, and have not yet been able to find it. I have a 2000 Cherokee with 147000 miles on it. We bought the car new. Oil and filter every 3000 miles. Coolant flush once a year. Recently the engine started to overheat. I replaced the radiator and cap, the water pump, fan clutch, thermostat, hoses, overflow tank with hose and the coolant temp sensor. It still overheats. Just coming off of a diesel engine switch in my truck, I at my age can't get into another heavy duty job. Suspecting at least a head gasket, I took the jeep to a trusted shop. They checked for coolant in the oil, oil in the coolant. Nothing found. Suspecting a blocked head gasket, they pulled the head. The gasket is fine and the head passed pressure testing at the machine shop. The only thing that they found was a .03 warpage. We will have them re-surface the head and re-assemble. I'm very concerned that nothing has been found, and that we will have the same problem when it's re-assembled. Are we missing anything here or is it time to pay a $1500 bill and throw the car away?

Peter

 

At this point you might as well see if they can check the block for cracks and insist they meticulously clean out the coolant passages before reassembly.

What is the behavior of the overheating? Did you verify that the gauge was reading the temperature correctly (in other words, did you check with an IR temp gun)? (No offense, just requisite standard simple stuff check).

 

For me, whenever the factory 0331 cylinder head comes off, it doesn't go back on. Because of the factory defect between cylinders 3-4 which can lead to cracking no matter how good your maintenance is. Clearwater Cylinder Head offers great heads without that defect. Just a thought...

 

It behaves as though there is some sort of a blockage intermittently. Yes I did check it with my IR gun. It has the normal difference between top and bottom hose at idle. The thermostat opens at exactly 195. The system does not lose coolant until overheat. In town driving or on the highway, but not at idle. Doesn't make any sense to me. And yes, if I knew that the head was cracked, I would replace with one from Clearwater. But the shop says that the head is not cracked.
Peter

 

Replace it anyway....like said above. Once it came off, it should have never gone back on

 

Whenever I see a post where the entire cooling system has been overhauled on a vehicle that previously had no overheating problem, and the motor/head doesn't seem to be implicated, I wonder how often the transmission gets checked for temperature. It shares the radiator, and if something is wrong with it that is causing it to go nuclear hot, it could present as hot engine coolant temperature. Can the old-timers check me if I'm wrong about this?

 

You might have a blockage in your heater core. Its a open system so it might be worth a look. Have had it happen on a couple of XJ's i jave owned

 

About 4 years ago the heater core started to leak. I bypassed the heater with some copper.

 

With those symptoms, along with the parts that you have replaced, I'd still suspect the head. (even though it checks out ok supposedly)

 

If there were a crack you could probably see it when you look in through the oil fill cap hole. A friend of mine bought a 2000 and once all the sludge was cleared away you could see it clear as day.

 

The O.P. mentioned he hasn't (or hadn't at the time of the original post) had it back post head machining.

As far as the "not putting the orig 0331 head back in, even if it's not cracked", I agree with the other folks that say don't do it - get a clearwater (or other reputable rebuilder brand) head.

I can say that I drove a 00 TJ for 14 years as my DD, had a couple of overheating issues and after 302k miles never had it crack. My buddy recently bought it and the engine still runs great and remains crack-free. I do think this is the exception rather than the rule however, but I mention it just as an example that the original 0331 CAN go the distance without failing. I would advise the replacement, despite my experiences, only because you don't want to sink a ton of money into the head only to have it crack a month later.

 

I've had a couple XJ's myself with the notorious 0331 head, I haven't had any crack as of yet.....(knock on wood) However, I also have a '99 XJ with the 0630 head and that one has either a blown head gasket or cracked head (coolant in oil)

 

What I would do if it were me ---

If you've already sunk a ton of money into preparing and re-installing the old head - AND you are comfortable with close monitoring of your engine (like a blackstone oil analysis every single oil change plus routine visual checks) - AND you are willing and able to replace the head yourself if it cracks - THEN go ahead and re-install.
If even one of those conditions are not true - then bite the bullet and have a clearwater head (they're about $500, so compared to labor, not the end of the world in terms of cost) delivered to the shop and have them install it rather than the old head.

It's an odds game that is really not in your favor (I'd put it at a 20% chance the old head will be ok.. and only that high because it hasn't cracked already) keeping the head. However, you may get lucky and be one of those (like myself and Jeepy) that dodged the bullet.

 

Also, do not throw the vehicle away. I will gladly take it off your hands if you no longer want it.