So I drove a jeep today, a 2001. Ran well, but I'm on guard for those damn head cracks. I cold started it just fine and the pressure was nearing 40psi. After about 15 minutes and a quick drive it went down to only about 10psi. That seemed to start when I shifted into 4wd. Once I was back on the road the pressure rose, slightly, to around 15 or 20 psi and would go back down when I was stopped. Should this concern me or is this common?

 

So is the oil pressure pretty steady when idle and when driving? If the needle is bouncing around you could have a bad sender. Typically when the engine is at operating temp the pressure will drop at idle. That is normal. If your oil pressure is zero and the "check gauges" light comes on THEN you should worry...

One thing you didn't mention is what weight oil you are using?

 

Yea, the pressure seemed stable at whatever I was doing. I didn't notice any bouncing around. It started about mid gauge and then once it warmed up went down to the bottom of the gauge.

 

2000 & 2001 are noted for low oil pressure for the following common causes:

1. Cam bearing walking out of journal
2. Head gasket leaking glycol into oil
3. Cracked head leaking glycol into oil
4. Worn lifter bore
5. No explanation

Number 1,4 and 5 can be tolerated w/o any ill effect.
Number 2 and 3 require immediate attention!

Mine (2004 with a 2000 salvage engine) has been running for years with 4psi

 

Just had this in my xj. It was the sending unit.m 40 bucks at OReilly. Get the special socket or u will be fighting it with channel locks like I did

 

No one should rely on the dash gauge for accurate reading, it is a two dollar piece of crap good only for laughs and giggles.

 

You just doubled the value of that cheap piece of crap gauge, maybe even tripled it.

 

4 psi? That's according to your "two dollar piece of crap good only for laughs and giggles" dash gauge, I assume?

I suspect an accurate gauge would tell a different story. I can't imagine an engine surviving very long on 4 psi of oil pressure.

 

10/40, lucas, stp, zmmax, CD2 and maybe some marvel for good measure lol i think the "rule of thumb" is 10psi per 1000 rpm.. i think..

 

Have you VERIFIED the pressure gauge is accurate with a mechanical tester? Very frequently the sending units are clobbered. Also the passage to the sensor can be gummed up and not allow for an accurate reading.

Oil filter is what brand and how old?

Cheap things first...

 

Verified with real gauge. Pressure alone doesn't tell the real story. You can still have oil flow and that is what matters.