Rear Main Seal Leak

[drase]

My rear main seal is dripping 1-3 drops of oil when I park it every couple of times I drive it. My mechanic said he can replace the seal but it may not make much difference due to the design of the seal. He said they are just prone to leaks. Is this true? When others have replaced the rear main seal does it completely stop the oil leak?

[Blue XJ]

Mine stopped the leak, they have different seals out there, I think it was a dual lip seal that I bought.  It has a second lip in it that rides on a new piece of metal so it stops the leak.   A lot of times the seal ends up wearing a groove in the crankshaft and if you just replace the seal, it doesn't fix the leak because the groove is still there.   With the double lip seal, it rides in a different spot on the crank.

[Oizarod115]

what appears to be a RMS leak can be one or a combination of three seals.

1. valve cover gasket

2. oil filter adapter

3. RMS

 

if you plan on having the RMS replaced I would at least inspect the other two realllly well to make sure they are dry first. I've put new RMS in 3 different jeeps and it each one is dry as a bone now.

[pitbull4x4]

My 89,4.0 was leaking oil. Changed valve cover gasket, checked oil filter after oil change and plug. Still leaking bad, about quart every 2 weeks. Changed rear main seal. No more leacks. Also changed trans filter, gasket. Truck was on jackstands anyway. Lol

[drase]

Thanks for the info, picked up the MJ today and he clarified that something about the bearings can wear and the new seal sometimes won't stop it and basically what Blue XJ stated.

 

Oil is leaking from valve cover and RMS. I will replace valve cover but don't have the knowledge to do RMS. He said the valve cover might stop most of it. We'll see.

[cruiser54]

Thanks for the info, picked up the MJ today and he clarified that something about the bearings can wear and the new seal sometimes won't stop it and basically what Blue XJ stated.

 

Oil is leaking from valve cover and RMS. I will replace valve cover but don't have the knowledge to do RMS. He said the valve cover might stop most of it. We'll see.

What you're describing is PRECISELY why I wrote this:

 

 

 

 

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, people on Jeep forums who can’t see your Jeep from where they’re at, 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. "$hit 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. 

 

Revised 02-26-2013

[metrictonner]

Yea, there are all sorts of leaks that can appear to be the rear main seal.  The one that finally cured mine was replacing the clutch line from the master cylinder to the bell housing.  The rubber part was bad.  DOT3 can do a good job of cleaning the junk down there and making it appear to be oil.  Try a new oil pan filler plug gasket too.  These are special metal washers that never get replaced.