I just replaced the rear main seal and oil pan gasket.
I still have oil dripping from the middle and passenger side starter screw on the inspection plate. How do I diagnose a rear main seal leak? I have already checked all the other potential leaking parts (valve cover, distributer, oil filter, oil filter adapter, oil pressure sending unit, ect,) what else could this be? How do I know for sure it's the rear main seal???

 

Spray the engine down with brake cleaner and let it dry. Then take it out for a short drive and come back and inspect the engine to see where oil is coming from.

 

I did that. The only place that is wet is the side of the block where the dipstick is mounted. Impossible to see if its leaking down the back because that side of the engine isn't visible.

 

CRUISER'S MOSTLY RENIX TIPS

REAR MAIN SEAL DIAGNOSIS

OCTOBER 31, 2015 SALAD 3 COMMENTS

I’d be looking up ABOVE first, and VERIFYING the source of the oil leak YOURSELF.

Everybody, who doesn’t own or have to pay for or perform your vehicle repairs, loves to poke their noggin UNDER the Jeep and come out bearing the false bad news that your RMS is leaking. Many mechanics, friends, and good old Uncle Bob seem to enjoy telling you it’s the rear main seal. Has a catastrophic ring to it, doesn’t it?

A simple leak at the back of the valve cover or other source could produce the same symptoms. You don’t need to be a mechanic to figure this out. If you have good eyesight and a dim flashlight, you’re good to go on your own. Don’t jump on the RMS/oil pan gasket bandwagon right off the bat.

Almost any oil leak on your 4.0 is gonna drip from the RMS area for two simple reasons:

First off, the engine sits nose-up and any oil will run back to the RMS area.

Secondly, the RMS area is also the lowest point on the engine. Simple physics and the old plumber’s adage apply here: “Crap flows downhill”.

Valve cover gasket, oil pressure sending unit, oil filter adapter seals and distributor gasket, in that order, have to be eliminated as possibilities first. A little tip here. Rather than use a dizzy gasket, use an o ring instead. NAPA #727-2024. Tips 12 and 13 will help you get your distributor back in place correctly.