There seems to be an awful lot of conflicting information about oil pans and high volume oil pump installation on this forum. I’ve heard the pan slips right out, you have to droop the suspension, or you have to raise the suspension, you have to disconnect the shocks, or maybe the steering stabilizer, or you have to take out the engine mounts. Some say remove the starter, some say the exhaust, some say both. With regard to the high volume pump (setting aside the question of whether it’s a good idea or necessary), I’ve read that it drops right in, or it hits the crankshaft, or it hits the pan. Melling says "exact fit", but then says to "check crankshaft and oil pan clearance." I don’t know if the differing experiences are due to model year differences, or manufacturing variations, or what, but here are my experiences doing the job on my 2000 Cherokee. YMMV.

I did it for the usual reason (low oil pressure due to coolant contamination from a now-replaced cracked head), and it was one of those messy jobs from hell, requiring considerably more than the four hours I’ve heard quoted. The arthritis in my wrists and fingers didn’t help, either. Starting with several very stuck lug nuts, I bent the lug wrench, penetrating oil and an impact wrench still wouldn’t move them, finally a breaker bar got them suckers off… the studs were fine but the tapered nut faces were rusty.

Maybe the pan can come out without removing the starter, but it would be a lot tougher, so I unbolted it. I didn’t touch the exhaust. With the wheels off and jackstands under the frame, the pan still wasn’t coming out, no way; it needed at least another inch at the back. I was able to push it far enough sideways to remove the pump, hoping it was just the pickup screen holding it up, but still no joy. I considered leaving it there and installing the pump that way, but it would be near impossible to check the clearance.

Around this time I got hit with a stomach bug, so I quit for the day… getting sick while laying on my back under a car is not a pleasant scenario.

The FSM says remove the engine mount through bolts and jack the engine up, the Haynes manual says to disconnect the steering stabilizer and shocks. The engine mounts looked easier, so that’s what I did the next morning… and after lifting the engine an inch or so, the pan slipped right out.

That’s a good thing, because with the pan out I could see where the larger pump was definitely hitting the crankshaft. I milled about .050” off the high spot on the casting, and then it fit fine. I didn’t pack it with Vaseline as some have suggested, but I did fill it with oil before bolting it in place for the last time.

The new pump also interfered with the pan. I cleaned and marked the pan with Dykem Blue to see where it was hitting, and it was only a small bit of beating with a ball peen hammer to eliminate the interference. I made sure it fit without the pan gasket so I would be assured of adequate clearance when the gasket was installed.

The Felpro pan gasket comes with these nifty little threaded plugs to hold the gasket in place while the pan is installed, instead of the cutoff bolts the FSM shows. Unfortunately, the front ones are too long to get the pan in past the front axle, so I had to pull them before the pan was in place, but the silicone on the corners held it adequately while I maneuvered the pan into position.

I considered replacing the rear main seal while I was in there, but I opted for the “if it ain’t broke, don’t fix it” approach.

The rest of the job was uneventful if tedious. Lots of recleaning parts because I was doing all this laying on my back on a sand driveway. With everything back together, fresh oil and a new Pur One filter, I disconnected the crank position sensor and cranked the engine for 30 seconds or so. Didn’t see oil pressure while cranking, but I went ahead and reconnected the CPS, started the engine, and had oil pressure almost immediately… 45 psi at cold idle. With the engine warm, I’m now seeing about 50% higher oil pressure than before at all rpms (a bit over 30 psi at 2000 rpm where it used to be a bit under 20, and 10-12 psi hot idle where it used to drop to zero with a “check gauges” light). Still not wonderful and still below specs, and I know it’s a band-aid mainly to make me feel good, but I’m glad I did it. Hopefully the extra supply of oil will at least delay further wear of the cam bearings.

 

Wow...Glad you lived through that! I'm going after my RM soon, have that and the gasket here. On my stock 90 I'm hoping I can just disconnect the top shock mounts and drop the axle enough to get the pan out. (with the starter out).

 

Just came across this old thread, I should update... 2½ years and quite a few miles later, oil pressure is the same, engine is still running strong, some valve noise at low rpm but it hasn't gotten any worse. So a worthwhile fix.

 

A.

 

Thanks for the follow-up!

 

Yeah, always enjoy reading follow up posts, helps bring things fill circle and confirm results

Glad your 4.0 is still running strong!

 

I've got to be honest and fess up. Probably dumb of me, I had two 8 ton bottle jacks handy. With the shocks undone I still couldn't get the pan out. Instead of trying a smarter angle, (like maybe the pan could have fit out if I changed something), Instead I used those two jacks. The end result is OK for me, but not a customer. Seems I bent the "studs?" whatever the anti-sway bar fits to. Seems fine enough, but sloppy work i WOULDN'T WANT TO PUT MY NAME ON!

 

I recently paid a shop to do this job for me plus RMS. Its now leaking oil from the oil. It's only been about 3500 miles. With the oil pump did you have to bang out the oil pan to make room for it?

 

Been 5 years so I don't remember, but I said "Melling" in the first post so I guess that's the brand. I don't remember where I bought it, probably Advance Auto but it might have been online. It was still running fine when I sold the truck a few years ago.

 

You must beat the pan like crazy to get the clearance for the high volume oil pump which is not needed anyway.

 

Sad you sold it.

 

In my case it didn't take all that much bashing... and the high volume pump DID fix my problem so I guess it WAS needed. YMMV