LemonXJ

New owner of an 01 xj with the 4.0
All stock automatic with 96~k on it great condition other than one thing.

I bought it with the dreaded 0331 cylinder head, and when it arrived I found it already with the mystery oil leak, low pressure at operating temps, milky oil etc.
so it's obviously cracked, need an opinion on if I replace the head and move on, or spend the money for a re manufactured 4.0

Jeepin'_Aint_EZ

Really depends on how long it's been driven like that. Coolant mixed oil isn't going to make the bearings happy so you could always pull the pan and check the bearings out. Little plastigauge to measure clearances. If everything checks out good, throw a reman clearwater head on and call it a day.

Ben Reilly

Agreed, If your bottom end is still good I would do a head and lifters.

Firestorm500

Milky oil has wiped the bearings. Since the oil is milky, a lot of coolant has been in there a long time. The cam bearings are the first ones to go. They are the most critical to oil pressure. Plastigauge won't help there.

Do the whole thing or pass it on.

KD3NE

Years ago I had a problem ..... was loosing coolant but saw no signs of a leak.

Checked the oil and not only did I have more oil in there than I should, but it looked like chocolate milk as well.

Coolant was leaking into the crank and I had been driving it like that for a while.

Was a head gasket problem.

Pulled the heads, and replaced the gaskets .... did nothing with the motor.

Put it all back together ..... filled with coolant and oil.

Fired it up and drove off like nothing happened.

Oil pressure was fine ..... it dropped a bit when at temp, but never below say 20 psi.

Milky oil does always mean wiped bearings ..... but it does mean you should check them out.

I would replace the head and run it for a while paying close attention to that oil pressure.


What I would do in your case ....... replace the head, and run it.

If the bottom end is bad, you can always buy a reman short block without the head and use your new head on that block.


I am no fan of using the proverbial Parts Cannon!

mikesignal

^^ I would agree. get a clearwater head for $450 and put it in. After you put the new head on , you can get an oil analysis done, and do further testing if you want. oil analysis can show metals in your oil and give you a clue if something is worn/wearing bad. Also investing in the new head, as stated above , can be used in a new motor if this one turns out to be bad. You can also get an oil analysis done now, but not sure how good of a test it's going to be with that much coolant in it. I would contact Blackstone or another analysis company and ask them. Also not sure what your oil pressure is, but I'm almost positive the book says 20 as a low point.

http://www.blackstone-labs.com/

Firestorm500

I don't like to do the same work twice. Or more. I don't have time for it. Don't want to spend the extra money redoing stuff, either.

Others do, apparently.

nujeepguy

how much for reman 4.0?

mikesignal

I think they around 2k, and probably a $500 core charge........You can go to a junk yard and get a used 4.0. I think the place by me they are $300. You need the 0331 head for a 2000-2001 to fit the manifolds and the coil rail, unless you want to make a bracket for the coil rail. They might make a converter from the 0630 head to the 2001 manifolds, but not sure. Thats why I was saying to get the cleawater head anyway. Another option is to try and find a beat up jeep with a good motor cheap. My neighbor had a real beater but it had 30k on a rebuild (1994). He said he wanted $500 for it, but I had no need for it. He has since sold it.

extrashaky

How low?

If it's dropping to zero at hot idle, and you have confirmed it with a mechanical gauge, it probably does have bearing damage. At that point it's hard to justify putting a new head on a spent block. If it's not dropping to zero, it may not be too far gone to save.

There is a guy who makes an adapter, but apparently you don't actually need it as long as you use the correct manifold gasket. The issue is that the 0630 exhaust ports are bigger and can leak exhaust if they aren't covered. I can't ever remember which gasket you need to prevent that. I think it's the 2001 gasket, but I would suggest double checking before taking my word for it.

As for the coil rail, you can make a bracket to hold it in place, or you can always just install a Dodge or Chrysler six cylinder coil pack with spark plug wires to get rid of the coil rail altogether. Most people mount the coil pack on the overflow bottle, extend the coil wire from the firewall and cut plug wires to fit. Search "Viper coil conversion" for more info on that.

Turbo X_J

If you disassemble a re-manufactured long block like a Jasper, the warranty is void. Best answer if necessary is a new or different engine or for that matter a different vehicle entirely.

kgm

Yeah I'd check oil pressure with a mechanical gauge and go from there. If it is operable, I'd spend the money and keep it going. If it's hitting real zero, your bearings are toast and there's no reason to replace the head without replacing the whole shebang.

mikesignal

I should have said , "new to you", or used, motor. Not a brand new motor. I was thinking junk yard or used motor

Firestorm500

Some time ago I was was quoted $3,200 for a Jasper engine with a 3-year warranty. This was for a '92 type 4.0 with my core being good.

extrashaky

Jeez, the base price of the Golen stroker for a '92 is $4,000. $3200 for a stock 4.0L doesn't really seem like all that great a deal.