You are correct in that everyone should know the potential failure issue with the 0331 cylinder head. Will all 0331 heads crack? Absolutely not. But enough do that if you own an 00-01, you are in denial if you say this isn't an issue. It is an issue. And while an overheat virtually guarantees a cracked head, you can have a cracked head even with perfect maintenance.

My recommendations continues to be this. Be sure all cooling system components are up to snuff. Every single one. Lift the darn hood once a week and check the coolant level in the coolant reservoir. Takes all of what, 30 seconds? The reason this is extra important with the 00-01 is this:

THE #1 SYMPTOM OF A CRACKED 0331 HEAD IS UNEXPLAINED COOLANT LOSS.

Commit this last sentence to your memory!

You shouldn't have to add coolant to your coolant reservoir. If you do, you're either leaking it or burning it. If you are having to add coolant, start with a comprehensive search for a coolant leak; get under the vehicle with a good light. You don't want to overreact because you have a simple radiator leak!

If you do confirm that you have a cracked head, don't continue to drive it. Replace the head ASAP, change your oil and filter a couple of times and you'll continue to enjoy your XJ. If you don't catch it early enough, the coolant mixes with the oil and toasts your engine bearings.

Then it's rebuild or find a remanufactured or salvage yard engine.

Dead on info BUT if you do find out that your bearings are shot there is a good chance that the crank is still good. IF this is the case you are looking at a $100 repair if you do the work yourself and you do not need to pull the engine. Unfortunately you cannot replace the cam bearings as easy but the cam bearing are not as critical as the crank bearings unless they have spun. You may still end up with lower than normal oil pressure at idle but you will still have oil flow and that is all you need to get lubricant to the bearings and lifters and rockers. I have heard stories of the 4.0 running well over 100k with low oil pressure. No LOUDknocking is a good sign.

You guys are going to drive me to drinking! I looked all over the head including in the oil filler hole and all I could find was a "DD".


I warmed up the engine which sounds strong to me (no knocks) and took pictures of the gauges.


@ idle - 30 psi.


@ 2,000 rpm - 50 psi. Now, tell me something good!

GOOD! mine reads zero at idle and it is my DD I don't worry about any more but the chime is annoying. Anybody know how to dis-able it?

Does anybody know what the "DD" on my head means?

thats triple the oil pressure i have. my gauge reads 5-15psi hot idle. never checked with a "real" gauge though. but i have 245k on my xj

i wouldnt worry too much.