Rear main seal - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Wolf · 11-09-2008, 03:48 PM

Rebuilt my 270 and now the rear main seal is leaking. I'm so f...... pist, I'll have to take it back out agian. Any ideas why this could be leaking after rebuilding. Used a good seal from Fel-Pro.
I thought it would swell up and stop, but after I stop theres a good spot on the ground.
Anyone heard of a rubber seal? Can I use one for this and where can I get one.
Thanks

OrrieG · 11-09-2008, 04:21 PM

When you did the rebuild did you check the crank seal surface for any wear? Might not be the seal but the crank is worn enough to not properly seal. Just a thought.

Wolf · 11-09-2008, 05:05 PM

The crank was grinded and cleaned. All new bearings.

dwcsr · 11-09-2008, 05:54 PM

On the rear cap you need to put some RTV on the mating surface so it seals up the end of the engine. These old motors will leak around the seal.

I would do an in truck repair. just drop the pan and the rear cap and make sure you seal up the pan ends with RTV as well.

On the cap use just a very thin line of RTV 1/32 or less. You don't want to change the clearence on the bearing.

Wolf · 11-11-2008, 09:43 PM

Thank you.

mr48chev · 11-11-2008, 10:06 PM

You will probably have to loosen all of the main bolts to let the crank drop just enough to roll the top half of the seal out.
Make sure that the lip on the seal is installed in the correct direction too as I have followed behind someone who didn't and the rig had a big leak.

dwcsr · 11-12-2008, 12:08 AM

Quote:

Originally Posted by mr48chev

You will probably have to loosen all of the main bolts to let the crank drop just enough to roll the top half of the seal out.
Make sure that the lip on the seal is installed in the correct direction too as I have followed behind someone who didn't and the rig had a big leak.

Very good point. Its one of the biggest reasons for a leaking seal after a rebuild. I just assumed you used a rope seal but most kits these days use the lip type inserts and not a rope seal.

11-09-2008, 03:48 PM	#1
Wolf Registered User Join Date: Sep 2004 Location: worcester,ma Posts: 13	Rear main seal Rebuilt my 270 and now the rear main seal is leaking. I'm so f...... pist, I'll have to take it back out agian. Any ideas why this could be leaking after rebuilding. Used a good seal from Fel-Pro. I thought it would swell up and stop, but after I stop theres a good spot on the ground. Anyone heard of a rubber seal? Can I use one for this and where can I get one. Thanks

11-09-2008, 04:21 PM	#2
OrrieG Registered User Join Date: Jun 2006 Location: Idaho Posts: 8,800	Re: Rear main seal When you did the rebuild did you check the crank seal surface for any wear? Might not be the seal but the crank is worn enough to not properly seal. Just a thought. __________________ 1959 Chevy Short Fleetside w/ 74 4WD drive train (current project) OrrieG Build Thread 1964 Chevelle Malibu w/ 355-350TH (daily driver) Helpful AD and TF Manual Site Old Car Manual Project

11-09-2008, 05:05 PM	#3
Wolf Registered User Join Date: Sep 2004 Location: worcester,ma Posts: 13	Re: Rear main seal The crank was grinded and cleaned. All new bearings.

11-09-2008, 05:54 PM	#4
dwcsr Hollister Road Co. Join Date: Apr 2005 Location: Houston Posts: 6,134	Re: Rear main seal On the rear cap you need to put some RTV on the mating surface so it seals up the end of the engine. These old motors will leak around the seal. I would do an in truck repair. just drop the pan and the rear cap and make sure you seal up the pan ends with RTV as well. On the cap use just a very thin line of RTV 1/32 or less. You don't want to change the clearence on the bearing.

11-11-2008, 09:43 PM	#5
Wolf Registered User Join Date: Sep 2004 Location: worcester,ma Posts: 13	Re: Rear main seal Thank you.

11-11-2008, 10:06 PM	#6
mr48chev Registered User Join Date: Jul 2007 Location: Toppenish, WA Posts: 15,413	Re: Rear main seal You will probably have to loosen all of the main bolts to let the crank drop just enough to roll the top half of the seal out. Make sure that the lip on the seal is installed in the correct direction too as I have followed behind someone who didn't and the rig had a big leak. Last edited by mr48chev; 11-11-2008 at 10:07 PM.



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