momentary oil pressure loss

[dungbeetle]

I was in my 97 Cherokee 4.0 following the Summit Machine group up AF canyon towards Forest Lake a week or so ago. I got to a place where the road was right by a creek and there was a post that said 194 on it, I think. Just then my oil pressure dropped to zero. I watched it for a second and it started to come back up, but then it went back down to zero. So, I shut the engine off and backed down the trail a hundred yards or so into a place I could turn around. I checked the oil, and it was full. So, I started it up and pulled onto the road pointing down, planning to turn the engine off and coast if necessary. However, the oil pressure had come back up to 40. So, I continued down the road and all the way back to Provo and never experienced another loss of oil pressure.

There was never any sign of oil pressure loss other than the gauge, i.e. the lifters never started clacking.

Trying to think of things to do before I go out again.

a) change the oil from 5-30 to 10-40?

b) install a mechanical oil pressure gauge to run in parallel?

c) pull the pan and look for some problem in the pickup?

Thinking of things that could explain the problem:

a) the engine is new, but was originally installed in a Grand Cherokee that was t-boned by an F350, so the engine has experience some jarring. It was recently installed by me in the Cherokee.

b) I recently installed a Teraflex oil pan skid plate

c) This is the first time I've ever run the car in 4 lo

???

 

[78mitsu]

I'd start with a physical guage. Then at least you will know if it's really the oil pressure dropping or a problem with the guage/sending unit.

 

[Cherokeester]

That same thing happens now and and then in my 97 TJ and seems to be a common problem with the 4.0. Change the oil pressure sender first as they seem to go bad and give false readings. Second, going to a little heavier oil would probably be a good idea.

You can find some more discussion on this subject here.

http://www.jeepforum.com/forum/showthread.php?t=595475

 

[ChestonScout]

Im guessing sending unit but it is possible the oil pump is going out.


I bought a v10 Ford a few years ago. On the way home from the dealership my pressure went to zero. Came back almost instantly, lasted about 5 minutes then went to zero again so I pulled over and called the dealer. He told me its just the sending unit and they will replace it for me. Started driviing home again with the gauge at zero. 5 minutes later it started making noise so I pulled off the freeway and the engine seized at the stop light.

I say put the mechanical gauge in and just keep a close eye on it for a bit

 

[TJDukit]

And stay away from Fords especially V10 Fords. And I agree with changing the sending unit and/or adding a mechanical guage.

 

[mbryson]

We've had two 4.0L Jeeps and have put 200K on one and 130K on the other. I've never had them drop to zero, but have had them drop from say 40 psi to 10 psi at idle quite regularly. Never had a 'real' problem with the engines. I'd chalk your experience up to Jeep engineering.

 

[1993yj]

My wife's Saab had that happen a few times before the engine blew on her while she was driving on the freeway. I think that the pump was trying to tell us something before it went out completely. Luckily it was still under warranty, but after that experience I would check as much as I could before having to buy a new engine. Problem with intermittent problems is that they never happen when you are trying to diagnose them. I think that Cheston's idea of the mechanical gauge is a good call.

 

[grandmaster]

I never had a problem losing oil pressure, but about 3 weeks ago my oil pressure guage was maxed out on the 80! so I put a sending unit in it and now its good and sits between 40 and 60

 

[dungbeetle]

After thinking this over and remembering how the oil ran off the dip stick like water, I think that the combination of 5-30 oil and the new oil pan skid plate plus the engine working hard going up an incline with little ground speed to give air movement... all that must have caused the oil to overheat and thin out...

Is there a combination oil temperature/oil pressure gauge available? What about an oil cooler?