Engine head question, 2000 XJ, 0331 head
 

My wife's 2000 Cherokee sport with 4.0 ran low coolant recently. I topped it off (took a little over a gallon) after motor cooled and it seems to run fine. Car only has 90K miles

There are no bubbles out of radiator, but it looks like there is a small amount of oil in the coolant. Does not seem to have coolant in oil.

So I call a local mechanic, who has a good reputation, and drives an XJ himself, to ask about cost of head replacement, since I read about the cracked head on this forum. He says he has never heard of the 0331 head problem, and has never had to do even a head gasket on one of these motors. Says a little oil in coolant not uncommon in an old jeep.

How common is the cracked head? Sometimes stuff gets blown out of proportion on internet, eg the famous "killer dowel pin" in the Cummins 5.9, which is a big problem, but actually fairly rare.

Welcome to CF..

The 0331 head problem is a well known issue.. Its a flaw in the casting.
The 0331 TUPY was the new upgraded head with the flaw fixed.

https://cimg2.ibsrv.net/gimg/www.che...1c974692a6.png




My 0331 head cracked..But some people go a long time without the head cracking.
Then people will say don't over heat it and you will be fine. Wrong, I never over heated my Jeep and it went. I purchased my 2000 Jeep new, had it shipped up to me here in AK.
So I know my Jeep was never over heated.



The head is flawed..I think give any non Tupy 0331 time, it will crack.

Original 0331 beads of water from crack between 3 and 4 cylinders.

https://cimg2.ibsrv.net/gimg/www.che...c0ebfdaf0c.jpg

You need a new mechanic

Read this from Shaky . Just him talking about the 0331 head.. He might chime in..lol

I'd be scared of your local mechanic if he's never heard of the 0331 cracked head issue. This issue is not the same as the KDP. I'd relate it more to a ford 6.0 powerstroke which are known for pushing head gaskets in stock form from the flawed factory head bolts. It's not a matter of if... it's when.

Thanks for the replies. I'm going to remove the valve cover this weekend and see if that dreaded crack is there. If it is not cracked in that spot between cylinders 3 & 4, there aren't any other known week spots in head are there?

When mine cracked, two reputable mechanics missed it, both saying it was a blown head gasket. One said it had to be the head gasket, because according to him the 4.0L is bulletproof, and the heads just don't crack like that.

It's actually not as widely known an issue as you'd think. People who drive older Jeeps or other vehicles never need to know about it and might not bother reading threads about the '00-'01. How many times have people who had owned Jeeps before posted here asking why their new-to-them 2000 XJ is losing coolant and overheating on the highway?

A mechanic can't know about every known flaw in every vehicle he might encounter. However, I wouldn't take his word on this:

Not unless it has a blown head gasket or a cracked head or block.

The 0331 head crack definitely does get blown out of proportion, because people generally don't run to the internet to post about the day their 0331 didn't crack. However, it's a real issue that should not be ignored or downplayed, especially given what you have told us:

The first question in your mind should be: Where did it go?

Unexplained coolant loss is often the first symptom of the 0331 crack. If it didn't leak out somewhere, there's a good chance it went into the engine, either into a combustion chamber or into the oil or both. If you don't look at the level in your overflow bottle very often, sometimes the first sign you get is that your Jeep overheats because too much coolant has been consumed.

It's not guaranteed that's what happened, but given the symptoms you already described, I would be looking for an explanation for that coolant loss. I would also be watching for the coolant level to continue dropping in the overflow bottle, and I would probably want to do some testing to try to rule out a head issue.

The only way to be sure of that is to send a sample off for analysis. I use Blackstone Labs. They charge $28 and will send you the sample kits for free. I now send a sample off at every oil change for all my vehicles.

Thirty years ago oil with coolant in it would turn milky. That's no longer the case. The detergent packages in modern oils can bond a lot more water than oil from a few decades ago, so that you often can't tell by looking at it that there's coolant in it.

If you have an air compressor, you might also want to do a cylinder leak down test (because a simple compression test may not be able to detect a crack). That can tell you if you have a crack through to the combustion chamber. You can borrow a leak down test kit from Auto Zone through their tool loan program if you don't have one.

Well, I join the 0331 club. The crack is leaking pretty badly, but thinking it opened up more the other day when it was overheated. Pretty sure it was leaking slowly before that. The oil pressure is good, and engine sounds OK, so I'm thinking lower end is not wrecked yet.

The drops of coolant in the first picture showed up seconds after starting motor. The crack is actually pretty long too, maybe shows up in second picture.

I see a couple places on line that sell rebuilt TUPYs, and few places with new castings. I read online that the new ones are mainly Chinese, So am leaning toward a rebuilt tupy. Seem like a safe way to go?

Seems like a pretty straightforward head replacement, its just that I was not supposed to have to work on this car. I try to stick to my old diesels, but now the family got me working on multiple "new" gas jobs, ugg first a 98 Volvo, now a 2000 Jeep.

The mechanic mentioned earlier said his approach would be to put in a used engine, but I figure it is likely to have same problem down the line, and would likely be of higher mileage than the car.

Took the valve cover off and confirmed head is cracked. Coolant seeps from and crack visible from the "normal" spot between 3rd & 4th cylinders.

Thinking of buying a rebuilt tupy head. Looks like most of the new heads on offer are from asia.

Sent up a similar post this afternoon with pictures of leak, more text, but maybe I'm too new on this forum to post pictures.

Sorry to hear it, but the silver lining is that it sounds like you caught it before the leaking coolant wiped your cam bearings. You still have good oil pressure, right?

A Tupy head is a good option. Alternately you can order a new head from Clearwater Cylinder Head in Florida. Tupy fixed the issue by adding nickel to the alloy to prevent the crack. Clearwater fixed the problem by making the deck thicker. The Clearwater head is a new Chinese casting, but so far I haven't heard any complaints about it. Either head will do the job.

Good luck!

The oil pressure is 40 PSI at idle cold, there are no bad sounds coming from lower end, and push rods spin as they should when motor is running, so I think bearings still OK.

Looks like a pretty straight forward head replacement, guess I'm going to have to do myself. The Jeep itself is in very good shape, clean and rust free, otherwise I probably would not bother. Glad I have this forum if any questions come up.

I purchased a brand new head from Clearwater cylinder heads last year and I have been happy with it.

https://www.cylinder-heads.com/autom...er-heads/jeep/

Ive had my Clearwater installed for 5yrs, zero issues. Super happy with it.

https://cimg7.ibsrv.net/gimg/www.che...82016b6cca.jpg

Keep your pushrods & rockers in order so they go back in their same positions.

I ended up buying a refurbished TUPY from 'heads only', a reman company I found on ebay. $425 including shipping and a return shipping for core.

Got the old head off yesterday and found the head was very recently replaced, apparently with a used 0331 head, new looking aftermarket gaskets, polished top of block..

The steel fuel line to rail broke where it bolts to manifold, it was rusty under the clamp, and probably was tweeked during last head replacement. Is it OK to patch with good quality rubber flex line? Am not too familiar with gasoline injected motors, and do not know the pressures involved.