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View Full Version : Curse of the leaking rear main seal..


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FrankNB
11-17-2004, 12:03 PM
I'm telling you.. I change that seal too often for my mental sanity... Before my rebuild, the only way it would not leak is with 15w40 and up.. Anything less would cause a leak...

We rebuilt the engine this summer, and I was told they polished the crank.. I've been running 10w30 since.. And, it's leaking again!! I bought some Esso XD-3 0w40 synthetic last night... It's alot cheaper than Mobil, but I hope that will be enough weight to stop the leak.. I don't feel like changing that seal with the cold season half started...

Am I the only one afflicted with 'The Curse of the rear main seal'? :(:

jeepsr4ever
11-17-2004, 12:09 PM
The rear main has these little oiling grooves in it to keep the seal from drying and wearing prematurely. Heat can cause a seal to hardned and leak. We added esther to the AMC-HD which keeps the seal soft and at its best sealing diameter. Synthetics these days have a small amount of this but might not be enough to keep your seal from leaking if your crank was to worn in that area. I would look to a additive of esther or a stop leak additive for a engine and that will keep your seal in good condition.

FrankNB
11-17-2004, 12:29 PM
Yea, you think a seal not even 6 months old can go bad that quick?? Gee, that sucks.. I believe the xd-3 is mainly a PAO base synthetic.. something like 70% PAO, and 30% esters.. Is there a brand of seal conditioning additive (besides using the HD AMC oil :wink: ) that you know works.. Just in case it still leaks after the change to 40 weight...

Although, now that I think of it... I had some heating problem after I dropped the engine in... my rad was shot, I put a 4 core and an oil cooler after that.. it got pretty warm, so probably damaged the seal then.. Maybe I'll change the seal before the oil change this Saturday.. would suck to waste a 60 oil change.. :!: :oops:

JesterTac
03-07-2005, 03:04 AM
Crank thrust issues can cause a rear main to live a short life too.

I know you rebuilt it in the summer, but I wonder if the guys at the rebuild shop did it correctly.....

My friend had a SBC that had the crank machined incorrectly and it ruined the motor and trashed his auto tranny as well because the crank was walking too far. And we all know how common SBC's are and how less common AMC's motors are......

JesterTac
03-07-2005, 03:08 AM
BTWay, your not the only one with the curse. My rear main lasted a total of about one week until it started marking its territory on the cardboard "catchall" on my garage floor.

Of course the bearings on my motor are worn down to the copper :lo1l:

I'm gonna abuse it till I get a raise or a cheap 360.

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