Oil Pressure Issue
 

I'mhoping you guys could help out with an issue I'm having...


Lastweek the engine of my 01 XJ started overheating, but never shut itself off. Itwould jump from about 220ish to 260, I'd pull over and put it in park and itwould almost instantly got down to 210 again. I added coolant andeverything was fine. But the coolant level dropped significantly again which iswhen I noticed a leak in the radiator. The oil pressure started dropping aswell and it's at 9/10 psi at idle and barely at 30 at 1600rpm (verified withmechanical gauge). I also couldn't get it to start once this week and alsonoticed some milky residue on the oil filler cap. The signs pointed to a possiblehead gasket issue, but it passed a block test at my mechanic’s shop. I’mswapping the radiator tomorrow, but am still left with the low oil pressureissue and the fact that it wouldn’t start this week (it has been very cold inMichigan recently but the no starting only happened once). Is it likely thatthere might be some bearing damage inside the engine even if the head gasketand cylinder head is intact? The oil pump is fairly new as well and mechanicruled it out. I did notice slightly lower oil pressure when it was warm beforeI had the overheating. Any suggestions what else it might be?

Cracked head.

Anti-freeze damaged the bearings.

Everything you posted so far points toward the 0331 head crack. The 0331 head used in the 2000 and 2001 XJ had a casting flaw that causes some of them to crack between the #3 and #4 cylinders. A block test wouldn't necessarily catch it if it cracked to the top, but the topside crack would allow coolant to leak into the oil, which then eats the cam bearings, resulting in low oil pressure. Sometimes you can even see the crack by shining a light down into the oil filler cap and looking at the top of the deck between the #3 and #4 cylinders.

I wouldn't throw any more big money at it until you verify whether you have a cracked head and how far gone the bearings are. 10 psi at hot idle is low but not dead (13 psi is considered minimum spec). It's possible the bearings still have life in them, and your oil pressure is being decreased by the coolant contaminating the oil. Have you tried changing the oil? If the pressure goes back to normal on fresh oil, you may be able to get by with just a head swap and still get some life out of the bottom end. Some people have also been able to bump up their oil pressure by going to 10W40. Or you could just be delaying the inevitable.

But either way, if the head is cracked, it either needs a head swap or an engine swap. Yours sounds like a borderline case. I wouldn't throw any money at the cooling system or anything else until that decision is made, since you may just decide it's time to send this one on to the boneyard or sell it rather than swap the motor, depending on your situation.