My Renix also has some oil pressure issues. After getting it up to about 210 and driving it the oil pressure drops to about 15-18 psi per the in dash guage and about 20 around 1500 rpm. Got a mech guage to check it today and if it looks bad I am gonna give the engine a good flush to see if it helps. If not I am gonna swap out to a high volume pump. If anyone has any suggestions or comments I am totally open to ideas. (I hate changing oil pumps, not hard just aggrivating on the XJ's)

 

Pull your valve cover it will give you an idea of how much sludge is built up. My 87 is running at 18-22 PSI. I am getting ready to pull the pan on that one but this was my valve cover



My oil pump is probably clogged with sludge like that. I plan on cleaning it all up. And then hoping I will get my oil pressure back.

 

If clogging is my only concern then I will be happy. I worry about bearing wear on the 4.0 with 172,000 miles. Without removing the cover you can see the rocker arms though the oil port and they look clean. But the cover is leaking anyway so a simple tear down and cleaning wont be too bad. If the mechanical guage reads in line with the dash guage then I am gonna drop the axle, remove the starter, drop the exhaust for clearance and pull the pan and pray that it looks good. The Renix runs pretty good right now. Nothing knocks or chatters, so heres to hoping the guage isnt reading right. I already replace the sending unit also.

 

High volume oil pump is for "volume" not for pressure! If you want pressure you will need a higher viscosity oil. JMHO!

BTW you don't need to remove all that to get the pan off. Just take down the rubberized apron on the lower end of the engine (if you still have one) and as XJStryker will attest, you can get the pan right off, after draining it of course. Just thought I would save you all that unneeded work.

 

I know the high volume pumps is for volume not pressure, but on previous vehicles changing to a high volume pump has increase dthe pressure some just due to the larger amount of oil being pushed though the engine. Example I can use is a good friend's, Brian, sister 88 XJ. The pressure had started to drop on her XJ and after trying a few things we decided on a hv oil pump. Now she stays @ 30 psi after warming up @ idle and around 45 off idle.

I dont know if the XJ has the rubbberized apron on it still or not. Her did and it made it a nightmare to get around. Thanks for the heads up BlueXJ, just saved me a lot of head aches.

I am debating on going ahead and order my 4.5 RC lift and do it all at once. Argh can make up my mind.

 

Lots of 4.0s with low oil pressure and no noise I've found have worn cam bearings and pressure is blleding off there. It's a pain because the engine has to come out and the head off to pull the cam and replace the bearings and a special installer is required. If you gotta pull the motor w/that many miles, it's time to rebuild.

 

Never tried to replace the cam bearings but have changed a cam without pulling the engine. Had to remove the radiator and the (non-working) condenser, head and lifters. Lifters came out a lot easier than I thought. Used a magnet and a piece of garden hose over the shaft of the magnet's handle. Put in a performance cam. What a waste of time and effort. The ECU negated all the work by altering the timing to compensate for the cams duration and lift. Oh well, any thing that don't work needs to be written off as a learning experiment.