Jeep Rear Main Seal Leak

[Nick1994]

On my ‘96 Cherokee 4.0L, I replaced the RMS myself about 10 years ago. It’s started to leak again this past year, getting much worse this past month.

I decided to take it to a local mechanic shop which I really like and have them replace it, which they did last week. They used a Mahle oil pan gasket and RMS. You don’t have to pull the transmission to replace it, the pan comes off (with struggle) and you take the rear bearing cap off and you can get to the RMS.

Well unfortunately it was still leaking, a bit better but still leaking. I took it on a long trip this weekend and then dropped it off at the shop this morning. They just called back and they’ve already got the whole transmission out to get a better look at it and sent me these pics. They’re going to replace the seal again, but this time with OEM seals. I told them to replace the oil pan too while they’re at it.

The mechanic is thinking if the crankshaft might have some wear, maybe it’s not sealing so good? What do you guys think? I really like this shop. They seem really honest and they go the extra mile so far, with other stuff too.

Second pic is the leak after it was replaced the first time. 3rd pic was before they worked on it.

 

[Nick1994]

Just got this picture, looks like there is a groove

 

[drtyler]

There are sleeves which fit into place to provide the seal a non-grooved surface. SKF calls them Speedi-Sleeves. That may be the fix.

https://vehicleaftermarket.skf.com/images/products/pdf/TT08_021_SPEEDI_SLEEVE_INSTALLATION.PDF

 

[The Critic]

If you have too much crankshaft end play, the rear main seal will continue to leak. Can you have them check into this?

 

[t1snwrbrdr12]

Likely not the problem as you’re seeing some wear on the crankshaft, but replace your crankcase ventilation valves atop the valve cover. My 96 XJ leaked out of the (original) rear main but cleared up after I replaced the valve cover gasket and vent valves. It made it till it was totaled at almost 260k without a leak.

 

[PontiacHO]

If you have too much crankshaft end play, the rear main seal will continue to leak. Can you have them check into this?

Yep. Thrust bearing and crank worn will cause the leak.

 

[t1snwrbrdr12]

And trusted shop of not (they seem thorough and good given they yanked the trans to get a better look) but there’s room for error in any seal installation. A Jeep 2 piece rear main is a bit tricky when you aren’t used to them.

 

[Soft Cars]

If the engine has ever been line bored, that'll cause and rear main seal leak too.

 

[Timmastertech]

Between the wear on the sealing face of the crankshaft (cant speedi-sleeve that design of crankshaft) and main bearing wear its unlikely that seal will seal.

 

[D60]

My parents have an '06 LJ with 25k miles that leaks considerably from RMS

I guess one could argue time waits for no rubber, but it's hard for me to not think the 4.0s just love to leak there.

 

[Chris142]

Someone got brutal with the seal and nicked the crank. That won't ever seal and you can't use a speedy sleeve there as someone mentioned. I always loosened all the main bearings a turn or so. That let's the crank drop and the seal can be replaced very easily. I don't know why others

 

[Chris142]

My parents have an '06 LJ with 25k miles that leaks considerably from RMS

I guess one could argue time waits for no rubber, but it's hard for me to not think the 4.0s just love to leak there.

Check the oil pan bolts nearest the 2 cats. They often come loose and look like a rear main leak.

 

[PontiacHO]

Back in the late 70s - early 80s at the Chevy dealer, we were told by the Chevy zone rep to install a .001 undersized bearing in the the rear main along with the new RMS. Everything was so poorly machined from the factory in those days that the thought was the undersized bearing would help keep the oil in the engine. Not sure that his idea was valid. I Pulled many 305s for crankshaft replacement under warranty for thrust knock.

 

[Nick1994]

Since this isn’t a bearing contact area, how can the crankshaft wear like this here?

 

[D60]

Since this isn’t a bearing contact area, how can the crankshaft wear like this here?

Because it's spinning in the seal and the seal theoretically grooves it?

Was that the question or did I misunderstand?

 

[PontiacHO]

I’ll add to the above…dirty oil helps groove the seal area.

 

[MattPersman]

Seals harden up and groove them. That’s a depends how bad the leak is scenario. Cardboard under it or gravel driveway just keep it topped off.

Very difficult for anyone to guarantee a leak free engine on one of those. Surprisingly the shop took that job in and is willing to try to redo it

 

[D60]

Seals harden up and groove them. That’s a depends how bad the leak is scenario. Cardboard under it or gravel driveway just keep it topped off.

Very difficult for anyone to guarantee a leak free engine on one of those. Surprisingly the shop took that job in and is willing to try to redo it

I agree. With forethought it would be best practice to warn the customer "we'll try our best but can't guarantee success"

However I am not hinting that OP is being unreasonable.

 

[Chris142]

Since this isn’t a bearing contact area, how can the crankshaft wear like this here?

It's very common. I'm more concerned about the nick I circled. Someone got brutal with the seal and damaged the crank. That's not normal wear there . You may be able to find a special seal that would ride on the ungroomed part of the crank but it's still going to be hitting that nick.

 

[Nick1994]

Just for it back, so far so good with new OEM seals and a new oil pan. I only paid $149 plus tax for a new OEM oil pan. Will put some miles on it and keep checking.