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Old 06-04-2012, 04:16 PM   #1
lowesguy
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Rear main seal again!

Did the rear main seal not to long ago,now leaking oil again! think the only thing I forgot to do was clean the crankshaft area with emery cloth,must have some deposits there that prematurely wore seal out.any tips on cleaning the shaft?
350 CI
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Old 06-04-2012, 07:57 PM   #2
Weasel Diesel
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Re: Rear main seal again!

Are you sure that its not the oil pan corners where the rubber half moon meets the cork gasket, then running down to the bottom of the cap looking like a R.M. leak? A dab of RTV is supposed to be there. I mean yes, it could be the crank either has a burr that is affecting the sealing area, or dirt or something.... or if it is a 1 piece seal, maybe got pinched going on...

Last edited by Weasel Diesel; 06-04-2012 at 08:03 PM.
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Old 06-05-2012, 01:04 AM   #3
wyattglock
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Re: Rear main seal again!

How is your pcv system? I have had that break the seal on gaskets before due to over pressure in the crankcase. Just a thought...
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Old 06-05-2012, 03:02 AM   #4
lowesguy
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Re: Rear main seal again!

Pvc systems good,my neighbor Rick a GM mechanic for 30 years told me I should have used some kind of strip paper around the mating surface at crank shaft,a ridge builds up over time and you have to clean it up or it will leak,dumb me I remember looking at that area and forgot to smooth it out! ,think my manual says to use some emery cloth .
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Old 06-06-2012, 09:28 AM   #5
Desert1957
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Re: Rear main seal again!

Please, DO NOT use "Emery Cloth" on your crankshaft. If you have to clean the surface , they make a 2000 grit paper that will not leave marks.

You didn't mention how many miles are on your engine , but if it has over 100k on it here are some things to check.

PVC system clogged as mentioned above ^^^^^

Other then an improperly installed seal.

Excessive crankshaft play (front to rear) will damage a seal in a very short time.

I have also seen , Synthetic motor oil used in a high mileage engine leak, due to it thin light weight properties.

I know its a difficult area to check for leaks while the engine is running , but be sure its the "Rear Main"

I have seen may oil pan gaskets leaking , which is usually the culprit.

I recommend the "Felpro" one piece style gasket, and make sure your oil pan rail is not distorted.

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Old 06-06-2012, 05:34 PM   #6
lowesguy
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Re: Rear main seal again!

I did use the Felpro gasket,and I installed it corectly ,didn't leak for a month, 132k on the truck,not sure about end play ,but probably has some.will recheck pvc system, soon as my shoulder starts feeling better
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