Oil Pressure, Round 2.

[Mike]

97 XJ 4.0

Recently, ive been noticing my oil pressure was kinda fucked. At 1800 rpms, it was at 37-40, and at idle, it would drop to 20.

Well now, Im at about 30 at 1800 rpms, and at idle, im at 10 fucking psi. What the fuck could be causing my oil pressure to drop so low?

I just did an oil change today, if that matters.

Heres a video, at the beginning, im at 1800 rpms, then I let off and it goes to an idle, then back up to 1800 rpm.

[88XJchief]

Did you use a fram oil filter? What weight oil are you running?

[Mike]

Yes, its a fram. It was doing this before the fram though, and I had a purolator.

5w-30

[88XJchief]

Time to go to thicker oil. Your bearings are going. I run 15w-40 and have 20 psi at hot idle.

[crosbike]

first off. dont trust that gauge. throw on a mechanical gauge to see what your engine is really doing.

[Mike]

Dec 23, 2008 21:47:51 GMT -5 crosbike said:

first off. dont trust that gauge. throw on a mechanical gauge to see what your engine is really doing.

yeah im gonna give the mechanical gauge a shot.


dont know if it matters, but I just went out and turned on the jeep. When the engine is cold, it idled at 35-37 psi.

Drove around for 10 minutes, got the temperature up to 210, and brought it home. At hot, it idled at 5.

[xjeeper]

i looked around a little bit and the oil pressure relief valve looks like it has been suspect several times on the 4.0 for similar issues. the valve is in the oil pump and is suppose to begin opening around 40psi to stop too much pressure from building up. sounds like it could be stuck open quite a bit.
i disagree that the bearings and clearances are causing it because they wouldnt cause it to randomly start acting up. a piece of debris plugging the valve would randomly cause it to change though.

[Mike]

it seems like temperature is a variable here. At cold start its pressure is 35-37

at 210 its 5

[Rico]

that means the oil is too thin, my old jeep had 13psi at all times, on a mechanical gauge and it still ran fine. just put 10w30 or 10w40 in it and drive it, but check it with a mech gauge first.

[Dr. Thunder]

Don't put 10-30 in it, all that's going to change is the cold weight which you are not having a problem with. Get some 5-40 or 10-40. Like I said before either a bearing is going (But you would probably hear noise) maybe your oil pump is wearing out, maybe it's bolts have loosened up (happened to me before) or like justin said could be a relief (which doesn't really make sense that it's letting it go to 37 when cold and only 10 when hot, a relief valve shouldn't car about temperature at all). Don't be scared to start it up yet, 10 psi is still enough to run an engine. If it gets much lower then you will not be able to start it and diagnose.

[Dr. Thunder]

And even though that oil is kinda thin it's not going to make a 30 psi difference at idle. Get rid of the fram also, purolators are better. Frams have been known to plug up and stop working, however I've never heard of them not working out of the box.

[Dr. Thunder]

So what happened with this thing?

[Mike]

havent had time to mess with it, In the last month that its been happening, its seen two, 1000 mile round trips to CT, and ive put 1000 on it just here in Virginia. It hasnt blown up yet.

First plan is to hook up a mechanical gauge, if all is well, I wont worry about it, if its fucked, im gonna switch the oil, change oil filters, and im gonna pull the oil pan and make sure all is well in there. Motors are cheap and so are XJ's. If i blow it up, i could part this one out and get another, or just get another 4.0.

[cntstpthestnk06]

so im kinda new to this forum but just to add my 2 cents. my oil pressure does the same thing. now i had noticed it right after i put a cold air intake in it and i took it out imidiatly. just cuz i dont wanna f it up anymore i figured bone stock is my best bet. but it still does it and i am running 10w30 i am gunna try 10w 40 next oil change and see if it makes a difference. if u do find out what it is LET ME KNO! so i can check mine too!