hey guys i need some help here my 4.0 cherokee's oil pressure is running at 80 psi while driving but when i stop and the jeep gos to an idle the pressure drops to 40 psi i have changed the filter but that did not help any ideas?

 

Let's trade engines...that'll fix it.

 

The oil pressure sending units fail in the most unusual ways... it could be your problem.

 

where is the sending unit located at

 

The sending unit is located right above the oil filter on left rear of the motor...Tj

 

hey guys i just wanted to thank every one that helped me i got the sending unit changed and so far so good thanks for the help

 

Hey all,
I'm having the same problem with my jeep. 96 4.0L is running with very high pressure around 45 at idle and then up it goes from there maxin out at 80 at higher speeds. I've already replaced the oil pressure sending unit no change. An engine whine has also developed and I've taken it to a place that spent an hour on it and still can't tell me what's wrong, but they can tell me my new gauge is working. They mentioned my oil pump might be the problem of gunk getting built up around the pressure valve. They want to charge me $800 to replace the oil pump If that 's it and I can't through that kinda dough right now. Any feedback would be greatly appreciated. Any ideas too

 

have you done a seafoam treatment on it?

 

do it your self just saying it's a lot cheeper. if you have a lift can't be to hard to get to. if not put a lift on it than do it

 

Is there any knocking? What weight engine oil are you using?

The whine and the pressure may or may not be related. The 94 Jeep I had always ran with a very high oil pressure as you describe.


IMO engine oil "treatments" aren't my cup of tea. They lower the oil's viscosity lowering the oil's ability to lubricate. It would be very hard on the bearing surfaces and piston rings. Instead change out your oil more often to see if the issue improves.

 

Go down to harbor freight and get yourself a mechanical oil gauge or oil pressure tester and take your sender out and screw in the gauge where your sender was and check the oil pressure.
Be careful and make sure you have adapters or that the gauge threads are the same as the senders threads, you could strip the threads on the block if it is not the same threads so check it very carefully.
Read what oil pressure tester says and compare them to your dash gauge after you put the sender back on, sometimes the dash gauges are not accurate.
Back in the old days we liked high oil pressure, ment the engine was getting oil everywhere, thats why us racers from way back would us 50 weight racing oil to get the oil pressure up, but with all these new synthetic oils that coat the engine parts better you dont need high oil pressure.

 

seafoam

 

??? Thanks for all your suggestions. I decided I'm gonna do an oil change first see if that does anything....if not off comes the pan. How can I check to see if my oil pump is bad? And someone else also suggested checking the oil pressure valve?? Not to sure where that is, but my manual is in the back at the shop due to the holiday weekend I finally get my xj back tomorrow.

 

ya the shop tested my sending unit is great. The dash guage is off but it's not by much.

 

you might what to drop you oil pan and pull your pump off and clean it. my 90 had a bad rear main and when i pulled the pan down we took the oil pump off that give us some room and i hand slug rocks in it, and it was making it read off by 10-15 psi.