After discovering a leak a few months ago, I replaced my rear main seal (69 Z28). I read up on here on all the tips and tricks. After replacing the seal it still leaks. What gives? There was at least one different looking seal available but I opted for the one that looked like the one I took out. Any advice for round 2 to try ensure a no leakage?

what kind of tips?? how bad a leak?? how did you seal the pan gasket at the corners where the rubber lip is?? if the crank is in good shape..i install the seals with a drop of anarobic sealer where the ends join...usually no problems...

More than likely, the leak is not coming from the rear main and it actually coming from the corners of the pan. I have the same issue. I have a slow leak at the rear of the pan. The corners of the gasket right on each side of the crank require RTV. Not much.

Did you put sealer between the main cap and block? I have a 454 that I thought the rear main seal was leaking. When I pull the main cap there was oil between cap and block. Seal wasn't leaking, but installed new seal and thin layer of permatex on the block. Also, put seal in so it doesn't line up with the seam of block and cap.

Using the one-piece pan gasket? It will cut down on those corner leaks as described.
X2 on using a sealer between the block & main cap. Not much is needed.

Sealer on ends like everyone mentioned but clocked the seal parting line in relation to main cap to block parting line, about 1/4" off the parting line will do.

I also use the one piece Felpro gasket and I put sealer in the main cap grove as well as a smear on the seal itself.
I have found that oil can and will be forced thru those sealing points.

Make sure you use the little plastic slips to roll the seal into the top part of the block. They come in the kit for that reason.

Also make sure you install the seal lip in the proper direction.

Cpz28
Just finished my real seal repair. Crank out to the crank grinder for a weld and polish.
Very long........ to get the motor back up and running used the new felpro viton (and a one piece gasket) like this; http://cgi.ebay.com/ebaymotors/Fel-Pro-Performance-2918-Rear-Main-Seal-2-Piece-Viton_W0QQitemZ220464896884QQcmdZViewItemQQimsxZ20 090810?IMSfp=TL0908101510004r14239
I have the engine on the a new engine run stand for cam break-in and leak check..just in case.

Todd

And a tiny dab of silicone on the ends of the seal where it butts together, trying not to get any near the lip. But if you do get some on it don't damage anything trying to clean it. I've taken them apart that had entirely too much silicone everywhere and wasn't causing problems, or leaking.

I just put some on the block back behind the bolts(don't put it up in the actual clamping area under the bolts) with my finger and wipe it off where it's almost invisible, then take a little screwdriver and apply a smidge on the seal ends and put the cap on.

Use a little machinists pocket rule to get the staggered seal ends the same height. I use about 3/8" because that's what all the cherry GM blocks I've checked have been but 1/4" may go together easier. 3/8 you have to kinda guide and persuade a little but it's not a big challenge. If I was under the car doing one then 1/4" would sound better.

I hand grooved my block so that it now has a little bitty groove under the rear main cap that channel's any oil back to the sump. (And also stagger the ends like a 1/4")...

Just looked fast at (6) of my books AND can't find a pic that shows how to do this modification??

Anybody got a pic or a link on how to do this??

I know I got this SOMEWHERE, but where????

pdq67

For small-blocks, the standard 2-piece Fel-Pro rear main seal is #2900 (blue, silicone). A much better one is the #2912 (fluoroelastomer), and if you have a wear groove on the rear main journal, they have a double-lip offset seal, #BS-118291.

:beers:

I just replaced my rear main seal and hope to get the motor back in tomorrow. I'm crossing my fingers.

I hand grooved my block so that it now has a little bitty groove under the rear main cap that channel's any oil back to the sump. (And also stagger the ends like a 1/4")...

Just looked fast at (6) of my books AND can't find a pic that shows how to do this modification??

Anybody got a pic or a link on how to do this??

I know I got this SOMEWHERE, but where????

pdq67
:thumbsup: Very good Cadillac did this from the factory back in the 60s thats how i learned.

Pressure in the crankcase?