Having established tonight that I do indeed have a cracked head on my 2000 XJ (I can see the tiny drops of coolant seeping in), I need to figure out what direction to go. It's otherwise in good shape, no rust, 146K. I know much of this has been discussed before, but I'm trying to clarify the best option for my own situation.

It's the typical thing, decent oil pressure (40) at startup, gradually goes down to 10psi per 1000 rpm as it warms. Right after I changed the oil (right after I bought the truck) it never went below 10 psi, but now with a few hundred miles since the oil change and, I guess, a fair amount of dilution, it drops down to near zero at idle and the light comes on, but comes right back up (10psi/1000rpm) with a bit of gas. Presumably with an oil change it would improve a bit.

When I bought the truck a few weeks ago, the oil gage sender was bad (read zero all the time), but I knew the senders had a bad reputation and since the engine wasn't making any noise and the oil looked OK with (supposedly) 2000 miles since the last change, I bought it. I guess I made a mistake.

Anyway, I know that an engine swap is the right thing to do... but it's winter here now, it's my DD, and though I've done a few in the past I really don't have the time or inclination to mess with a project of that size now. And, of course, there's the unknown with a junkyard engine. I could pay a shop to swap in an engine, but I'd certainly want a different year head, at least, which leads to other non standard things that I don't know if a shop would want to deal with.

I could, presumably, buy a rebuilt engine? From where, and what would one cost? I don't want a stroker or anything high performance, just something for a DD and light wheeling.

If I bought a rebuilt engine would it still have the 0331 head? If so I'd be asking for the same problems again, but an alternate head would required an aftermarket exhaust manifold, right? How would that work with California emissions? (I live in CT but apparently it has the CA emissions crap.)

It's not the "right thing to do", but if I just replaced the head (with a different year), with the low oil pressure I have now indicating worn bearings but no further dilution, how long could I expect it to keep running without major problems? As I said it's my DD, but only in the winter, so come spring I would be better able to deal with an engine swap or whatever.

A depressing evening...

 

I feel your pain. I'm in the same boat although I have a 99 with a 0630 head that is seaping into the valvetrain. I ordered a Clearwater head that addresses the 0331's weak areas. My oil pressure is better than yours so replacing the head was an easier decision for me. With any luck, it'll be finished on Friday as long as the other issues that plague my XJ are also resolved. If you do opt for replacing the head, I got mine through ebay, $415 shipped....

 

Check your compression. I'd replace the head either way, but you may be able to run it for a while in its current build. There are shortcuts to do only crank bearings but its a hoopty fix and only somewhat short term. Cam bearings will explode too over time.

 

Everybody seems to mention cam bearings in conjunction with low oil pressure, but not crank bearings?

 

I am here to ease some of your fear. Unless your oil turned milky your bearings are probably ok. What takes a beating is the cam bearings, mainly 3&4. That is because the UNDILUTED antifreeze is draining DIRECTLY into the lifter bores and camshaft. Cam bearings have the greatest effect on oil pressure. Now here is where alot are going to disagree but the 4.0 will survive with one or two bad cam bearings and low oil pressure.
I am a testament to your story...mine has only 4psi at 650rpm and only 20 at highway speed. It has ran this way for 5 years and over 50,000 miles. I purchased a salvage engine years ago so I would be ready when the engine blew....I'm still waiting for the knocking. It runs fine,uses no oil so I do not see the immediate need to swap it. Another variable is the type of coolant you used. Conventional antifreeze contains silicates (sand) this is what destroys the bearings. HOAT antifreeze contains a much lesser amount of silicates and universal (any make/any model type) contains NO silicates at all. If your engine is running fine and not making noise a head swap might be a quick alternative.

 

I was in a similar boat a few months ago except the PO disclosed that he had already replaced the head with a Clearwater and that he had low oil pressure. (2001 XJ 4.0, 133k) First thing I did was put in a mechanical gauge and yes it was indeed very low once hot. Low enough to trigger the dash light at idle, about 5psi on the gauge, and about 25psi at cruise, running 10w40 with ambient temps in the 70's. I sent off a sample to Blackstone and they indicated no metal was present that would normally be associated with bearing wear.

As fate would have it the next week someone local posted a new high volume Melling oil pump on Craigslist at about half the cost of new. I got it, a new Felpro gasket and rear main seal and did the swap. Also put on a Wix oil filter. Since then I get about 35psi at cruise, about 12psi at idle running the same oil. No noise from the engine, no abnormal usage, etc. Will probably send off another sample to Blackstone once I get to 5k on this oil change just for grins. I intend to just let it ride as long as the pressure stays where it is and there's no abnormal noises.

 

I have no doubt this is all true and I agree with most of it. A new head would that care of the current problem if in fact it is a very recent thing but I suspect it is much longer term than that and PO knew about it and reason for sale. The cam bearings are what affect the oil pressure the most but water in the oil does its damage in a lot of others also.


If you watch the engine very close I expect you can get additional mileage out of it just be careful that you don't damage other things like those needed for a rebuild on a low mileage engine like yours ie. the rotating assembly and block. This is just my feelings but I have always wanted a known engine to rebuild over one that may have been very abused.


I would switch to a different heavier weight oil if it were mine also.

 

My first jeep had this as well, and just like OP I could physically see the coolant pouring into the top end between 3 and 4 through the full hole.

I caught after maybe a couple weeks worth of low oil pressure and misfires. Wasn't as educated back then so figured it was heat soak.

i replaced it with a Clearwater, decided not to mess with the bottom end, and just run it until it dies, then just put a whole new(old) motor in, cheaper than rebuilding it where I was at the time.

I did like Fred said and ran Delo diesel weight oil, and put 50k miles on it before I started looking for a new build. Never a problem. Like others have said the bottom end isn't going to explode from a little coolant; unless it is discolored for driving for weeks on end like mentioned, then you prob have some real damage down there.

 

The low oil pressure right now is what worries me right now.
Has the pressure been verified yet?

 

This has already been explained...Oil pressure ain't going to help him overcome worn cam bearings. Pressure does not mean much in the scheme of lubrication. He still has the same volume of oil FLOWING through engine.

 

I guess I'll be cautiously optimistic... I changed the oil again this evening to reduce the ongoing damage until I can replace the head. Hot pressure seems a bit better, but I didn't drive it, I'll see how it behaves tomorrow. I'm reluctant to throw money (in the form of a new head) at what may be a hosed engine, but I suppose if then I do need a new engine I can buy a short block and use the new head on it.

Yes, I verified the low oil pressure with a mechanical gauge when I was fighting the gauge sender problem. I actually bought two aftermarket (Echlin) senders and both failed... the first indicated 10 psi whether the engine was running or not, and the second worked properly for a week and then went to zero and stayed there. Finally I bought a Mopar one and it's still working.

Everybody talks about Clearwater for a new head... is that the way to go? It's still an 0331, is that a concern?

 

The Clearwater head has areas "beefed up" so that the chronic 0331 head cracking should be a past worry. From my brief conversation with them, their head will fit both 0630 and the 0331 head (and one other that escapes me now). To my knowledge, it shouldn't be a concern. I'm having one installed now and can't wait to drive it and feel the improvement.

 

I wonder what Clearwater does with all the returned 0331 cores?

 

They are sent back to Spain where they are melted down to be reforged into new clearwater heads. Clearwater is an importer,not a manufacturer.

 

Just my thoughts...it's your winter beater, drive it and be prepared to have new bearings throughout installed, or swap in a new/used engine. It's not that difficult to pull the engine, knock out the bearings, install new with new rings. Best luck.