O.K. here it is, I have a 96 XJ with 176k on the clock and it just started losing oil pressure and low end knocking noise. I think it could be a wrist pin? took it apart and couldn't find anything using the usual methods and measusements and so went ahead and changed the rod and main bearings and the oil pump while I was in there. Also added a new Oil Pressure Sending Unit because I broke the original when installing the header. Put everything back together and no more lowend knocking but now a persistant tapping, like a valve tap and still low oil pressure - drops to about 20psi when warmed up with 10w20 oil. The tap does go away @ 1000 rpm but returns in a mojor way under load at anything over 1200rpms. As I remember correctly this engine always ran about 60psi oil pressure all the time until the last 5k miles. Oh yea, everything was super clean inside!

Any Ideas?

 

13 PSI is factory acceptable oil pressure at idle with a warm engine. 60 PSI all the time is not. A bad oil sender would cause the 60 PSI reading though.

What's your oil pressure at 3,000 RPM warm?


What brand of oil filter are you using?

 

I'm no guru, but try 10w30 instead of 10w20. It's factory spec, and such.

What brand oil and oil filter are you using?

 

Pressure @ 3000 is about 35-40psi with lots of lifter noise.

CORRECTION: I am using Brad Penn 10w30 Oil and an over sized K&N oil filter

 

Brad Penn 10w30 oil with oversized K&N Flter.

 

It's probably nothing to do with the weight of the oil but the fact that your lifters are all gummed up.