Ok you wise 4.0 gurus, I have a question. My 2001 xj Has the dreaded 0331 cylinder head and I think it may have gone south. I had it peg the temp gauge about 8 months ago and found the radiator had cracked causing fluid to depart. I caught it fast and then replaced the rad, water pump, and thermostat. It seemed ok but the last couple weeks it has been mysteriously losing all coolant. Not coming from any leaks and as far as I can tell, not out the tailpipe.
I found what looks to be mud in the new radiator as well.??.
jeep still drives ok, no weirdness. And the heater will run you out as long as it has coolant.
Help! Anyone have experience/advice on this?

 

check the oil and tell us what color it is.

Shine a flashlight down the oil fill hole on top of valve cover. And see if u can see greenish tint around the parts inside.

 

Mightb omtinghrrrrrrrrer> https://www.google.com/search?hl=en&...ts=&gws_rd=ssl

 

My 01 was using coolant. I had the oil tested at Blackstone and it showed coolant in it. Replaced the head with a Clearwater head and everything is good. That was a year ago and 15,000 miles later.

 

Well... I think the jeep just let me know more. Found a puddle of what looks like chocolate milk under the jeep this morning after it sat idling for a while. crap.
so....
what is the general consensus, new motor time? Pretty sure the bearings have been seeing water/AF. No running issues but this Isn't going to go away. Can't see buying a head and doing all that work to lose the bottom end. Plus the motor is at about 200k..
thoughts? Best rebuilt motor for the $$??

 

No matter what you need a head. Would buying/building a long block be much less than a head now and short block later if lower end is junk?

Most you would be out is gaskets/bolts

 

I don't think the time and costs would offset the possibility of the bearings going south. Wouldn't it be wiser to just say to heck with it and spring for new (rebuilt) and maybe get a few hundred thousand more miles?

 

By the time you are dumping in coolant all the time the damage is usually done - preventable owner neglect. Coolant is very corrosive to bearings. If caught soon enough there is no need to replace the block, only the head Reman engines aren't new engines like they put together at the factory. There are numerous people who have put in a reman engine only to have seals fail or other problems. Usually before warranty ends but its still a hassle.

 

The factory put together an engine with an 0331 head that cracks for no reason. I'm not sure a factory built engine is any better than one rebuilt by a reputable shop.

 

So if I order a remanufactured motor from someone, how do I make sure I don't end up with another 0331 head? What years/models of 4.0 will work with my 2001 that did not use the crap head??

 

There are actually two 0331 heads. The first one was offered on vehicles from late 1999 through 2002. In 2003 the 0331 TUPY revision was quietly introduced to solve the cracking problem. A TUPY head will have "TUPY" stamped into the casting between the #3 and #4 cylinders, right in the spot where the original 0331 head liked to crack. If the engine has the valve cover on it, you can see the TUPY stamp by looking right down inside the oil filler cap.

To be clear, you don't want the non-TUPY 0331, but a TUPY 0331 is fine.

The way you make sure you're not getting an original 0331 head from a rebuilder is to call them up and ask them what they're using. Get them to state unequivocally that they are not using original non-TUPY 0331s. Then check it when the crate arrives. If it arrives with a non-TUPY 0331, send it back.

I don't think you can even get the crack prone 0331s new, so anybody using one would have to be installing a used one. Most engine builders are not going to do that because they don't want to risk having the engine come back under warranty.

 

What does TUPY stand anyways?

Are there other aftermarket heads available?

 

It doesn't stand for anything. It's the name of a Brazilian foundry that made the heads.

 

You could go all out and buy the edelbrock aluminum cylinder head
Available early next year I think

 

check the oil pressure using a mechanical gauge with the engine cold as well as at hot operating temperature. Cold idle it should be no less than 40 psi and hot idle not less than 13 psi. Next do a compression test. They should read around 150+ psi and no more than 30 psi difference across all six holes. If all those measurements look good, get yourself a new Clearwater head - $480 dropped at your door step, slap it on a enjoy your revived XJ.