heres the prob first new oil and filter ,motor not gunked up on the inside .Start xj great oil pressure ,not over heatin no knock ar lifter tick after a few miles oil pressure starts to slowly drop to about 5 pounds, pull over sit for 5 minutes start back up ,drive a little oil pressure goes down again any body ever have this prob??????????????????

 

Jeez, did everybody just now find the oil pressure gauge on the dash? Screw in a manual oil pressure gauge and see what is really going on, then replace the sending unit. If you even think of replacing the oil pump to fix this non problem, I'll come over and slap you.

 

its not the uhit i did the manual gauge test same result thinking possible pressure spring issue in pump

 

If this symptom didn't exist before the first oil change, I think I would try a different filter.

What brand filter is this?

It may very well be something else, but I'd eliminate the filter before dropping the oil pan for that pump.

 

i changed the oil like a month ago this just happend to day ,needle just started dropping pulled over checked oil started had pressure 40 plus start driving then just starts dropping ??????????????

 

still looking for answer

 

still hanging around waiting

 

i got rid of my fram and went with stp this time but the filter is afer the pump if it is not allowin opil thru it , i would think the pressure would rise .

 

No leaks from anyplace that would affect oil pressure?

 

your not going to belive it but i have one of the very rare non leaking oil xj 4.0

 

You're not going to believe it, but it sounds like your main bearings are gone.

 

A long time ago I was changing my oil and broke the OEM oil pressure gauge down there by the filter. Got an aftermarket one and put it on. A while later I'am driving down the road and oil pressure goes to zero and light comes on. I check everything and its all good. Start back up and have oil pressure again and its all good. Some times pressure comes back up while driving. It does this from time to time. Not sure but could be the little plastic bubble that the oil pushes on to give a reading doesnt work all the time.

 

if main bearings were gone there would be knocking noise no ,have never heard of main bearings being good one minute and not the next.main bearings oil pressure would be low at all times ive benn in the automotive field for over 35 years semi retired now have never heard of any thing like this

 

plastic bubble ????? can you explain what you refering to

 

Have you made sure you've got enough oil in the engine? If the level gets too low it causes some pretty strange readings. I learned that the hard way and ended up with a collapsed lifter...

I wouldn't assume just because the gauge reads low that the main bearings are gone. Do you know how well the engine was taken care of over its lifetime?

Gauges can go out, sending units can fail. Start with the little, inexpensive things then work your way up from there.