Rear main seal leaking again after replacement

Hi,

I noticed you have been waiting for a specific person. However, I thought since it has been some time, I would try to help.

The first thing that comes to mind when you say it's leaking is the crankshaft end play. With a manual transmission, it isn't uncommon for the engagement of the clutch to apply additional pressure to the thrust bearing on the crankshaft.

This bearing is to limit the forward and backward movement of the crank. If there is excessive play, it will take out a seal or prevent one from sealing. Has the crankshaft end play been checked by the mechanic?

Joe

You are very welcome. One thing that people forget about is when you have a manual transmission, there is constant forward and back pressure on the flywheel (which is connected to the crankshaft). It's the nature of the design. Oftentimes, it causes additional wear to the thrust bearings on the crank allowing excessive forward and backward movement. Ultimately, you end up with leaks that just can't seem to be fixed.

If you have a chance, let me know what he says.

Take care of yourself.

Joe

Thanks J & N for jumping in here!

I got out of pocket for a while.

Here's the AMC Jeep manuals recommendations.

Adhere to the RTV application locations in their pic and also in the reading.

Return with good news!

The Medic

I don't know your mechanics abilities on the Jeep, he may have his own way of doing things (or not)

It's hard to say if the silicone was installed in the correct locations around the seal, there could have been misunderstandings with the manual's illustration.

Below I have traced in red the locations for the silicone to "dam" away escaping oil. Installing the seal "Dry" will not prevent leakages.

Other possible issues might be that the "Half moon" segment of the seal is being installed 180 degrees out from the way it should be--it's nearly impossible to get the other half of the seal wrong with the way it is made.

It is possible that the end of the crank could be damaged or worn, but even with some wear and a properly installed seal slight leaking might be tolerated, however if it is really excessively leaking, another crank might be in order

----The Medic

A way around replacing the crank could be a speedi sleeve if they make one in the correct size. Basically a thin stainless sleeve that is pressed and glued over the worn area of the crankshaft to increase it's size and remove the wear spots. Where I have run into rear main leaks past this type of seal was when an engine had been rebuilt and the folks who ground the crankshaft got a bit carried away and went to the maximum undersize. The OE seals in those would barely touch the seal surface on the crankshaft and you would get leaks in the areas that didn't have enough crush to make the seal. The old trick for that was to add a shim behind the seal to push it tighter against the crankshaft area. You apply a thin smear of permatex #2 to the shim and install it, then the seal section, then repeat on the main cap, apply the sealer to the specified areas and bolt it into place.
I've also seen the new "replacement" seals be made wrong, ran into that on a few small blocks with the early one piece seal. The seals were made with excess tolerance and would leak after about a week of running.
Perhaps have the mechanic try a test, with the current seal in there, clean off everything real well with some cleaner, now dust the area with baby powder or similar. Start the engine and see where the oil darkens the powder first. If it's at one of the parting lines then it could be a lack of sealant or the seal isn't seating correct. If it instead shows up at the seal lip where it rides on the crankshaft it is likely the seal isn't correct or the crankshaft has been ground so the seal no longer functions.
Lastly would be if the main bearings are worn in excess. That can cause the crankshaft to walk in the bearings and distort the seal enough that it can leak almost instantly because of that, it is more common with a manual transmission for the reasons stated above, a quick check of them using plastigauge would show that as well as any taper. Even looking on the rear main for it's size might help.

Well I'd like to say I'm surprised that an aftermarket part didn't fit, but I'm not. Seems to be a trend these days. At least you have it repaired. Thanks for the update.

Here's wasted funds on a really pretty valve cover.

Nearly all of the rocker arms smack/scrape on the side.

$30.00 and chromed was too tempting to let slip away. I kept it to show folks!

The Medic