Bryanvp74

I am replacing the valve gasket from prior owner who did a ****ty job as it is leaking out the back. I just bought this Cherokee with 138k miles. Oil pressure is low (like 12psi idling, maybe 15 when reving). Starting from the top before I pull the pan to first fix the valve cover leak, but then to diagnose the low pressure and make sure the train was getting oil as I hear some ticking inside the cover. So today I pulled the cover, I think it looks clean actually, but...a few questions:
1. Does this look like the rockers are getting enough oil? I had it running a few hours before this picture. I think maybe the low oil pressure is not allowing adequate splashing and is why those bridges have caked/burnt oil?
2. Should I pull the rockers to see if the push rods are clogged?
3. If all looks good, would you bother taking these rockers off and cleaning the bridges and pivots to get the bits of crud off? I was able to easily scrape a little off (don't want to do more while they are attached and get crap into the engine).
4. OR should I just put the new gasket on and call it a day??

Ultimately I need to figure out why I have such low oil pressure, so I am starting here and moving my way down. Already did a compression test, was great avg 160 across all 6. I am crossing my fingers that the the low pressure is due to a clogged screen in the pump or a bad pump.



Cylinder 6

Cylinder 5

Cylinder 4

Cylinder 3

Cylinder 2

Cylinder 1

exasemech

It's always helpful to give people a hint regarding which model year you have but it looks like it has a coil rail so likely a 2000 or 2001.

If that's the case, and given how clean it is in there, I doubt your oil pressure problem is a clogged screen. Google cracked 331 cylinder head, learn how to identify if that's what's in there and how to look for crack.

I also wonder, given how clean the head is, if that's a replacement head but the PO didn't fix the bearing problem

You might want to temporarily put a mechanical oil pressure gauge on it to confirm those oil pressures, if it's really 15psi at higher rpm you have a serious problem

Bryanvp74

My bad, I assumed my model and year were shown as I put that in when I created the profile. Yes, 2000 sport XJ Cherokee.

I didn't see any issue with compression. I didn't see any antifreeze in there or oil in the antifreeze. It's likely bearings or Cam I'm sure unfortunately. I was hoping for an easier fix...

Bryanvp74

I think you are probably right, about the new head and ignoring the bearings below. Why would someone bother with that? The head is pristine, definitely recently changed. No visible cracks

So I am going to drop the pan and just HOPE the pump is not good, but I think I'm probably kidding myself and I agree with you that it's likely Cam bearings. Going with hope, assuming it's a bad pump, how would I even verify that when I have the pan off? What would you look for? Also, should I do a plastiguage test on the main and rod bearings too? I guess if the engine is shot, before buying a crate engine (because the body has 0 rot or surface rust and has a great suspension and lift on it) I might as well give it one last chance with the stuff I can replace underneath for a few hundred bucks? What do you think?

Thanks

exasemech

1) unlikely it's the oil pump button check it you would get out your trusty shop manual and check the end play and other slop measurements on the gears. Probably more importantly, check that the pressure relief valve isn't stuck open and that the spring is ok.

2) it would be interesting to plastigauge the bearings and would give you a chance to look at the crank. When doing the main bearings you need to somehow lift the crank against the top shells ( the ones in the block)
As you mentioned it's likely the cam bearings but who knows. It might not be a total waste of time/ money to replace what you can and see what happens if the crank journals are good. You'll need to figure out what size bearings are in there.

It's also always possible the PO already did this.

awg

Whoa there, has anyone mentioned verifying oil pressure ? (they may have but i missed it)

While you have the lid of, I certainly would at least inspect a couple of push rods for anything unusual, do any suspect looking ones first, take no time at all

10 psi at idle is not hugely low but it should go much higher when revved, and I have found idle pressure will be very low if engine is worn internally (0-5psi)

hence rule out a dodgy sender/gauge

u have low miles and should not be worn out, although poor maintenance and many short runs can take a toll

Bryanvp74

Thank you. I will definitely check the pump as per your recommendations. Need to Google that procedure or get the Haynes and learn, confident I will figure it out, crossing fingers it's the pump. Will check the crank and bearing clearance too. Can you also check the Cam shaft/inspect cam bearings from underneath? Gonna take me probably a few weeks to get the pan down and do all this so I will follow up when I get there. For now my son is using it to drive to from school so it drives only a mile a day, it's gone this far I assume we're good for now.

Thank you. I did put a mechanical gauge on, but to be honest it was leaking a little from the connection point to engine block, so I will double check and do a better reading. It was definitely NOT going up more than a few PSI when I rec'd the engine. Should I also drive it and check while driving?

I did check the push rods. Besides the burnt oil on the rockers and bridge, the entire valve train looks brand new and clean, springs look new and the valve stems shiney and new too. I inspected a few rods and clean oil spilled easily out when I pulled them and they look straight as a pin. I look through from end to end and saw daylight. I was able to also spin the ones not engaged, etc. here are some more pics (cylinder 1 after I pulled the rockers and cleaned them. Did same for all 6 after).






Clean clean clean

exasemech

Check the thread, post #2. You really need to read before posting