rear main seal - revisited

[John G.]

While doing a timing curve check yesterday I noticed a pool of oil building up directly underneath the rear main seal area. After about 20 minutes of total engine run time the pool of oil on the driveway expanded to an area of about 3 inches in diameter. I've never had anything like this happen before.

The engine (327) is a fresh rebuild using a Fel Pro gasket set. RTV was used to seal the area on the rear main cap adjacent to the seal split.

I reread the thread from a couple of days ago where Joe Lucia recommended using the Fel Pro #2909 rear main seal. Looks like that will be the next stop.

Are there any opinions on what might have happened? ..

[Joe L.]

Re: rear main seal - revisited

John-----

I can almost guarantee you I know what happened. It's likely one of 3 things:

1) failure to apply sealer or failure to apply sealer properly to the rear main bearing cap and block surfaces adjacent to the seal ends as shown in the Chevrolet Service Manual. This is an ABSOLUTE MUST. Failure to do so will result in a leak virtually every time;

2) failure to install the seal properly or installing it backwards;

3) a worn sealing surface on the crankshaft journal.

[John G.]

Re: rear main seal - revisited

I sure hope I readily spot what I missed in the rear main seal installation .. Thanks for those reminders, Joe.

[H S.]

Re: rear main seal - revisited

Joe,
After tearing down the second time to find this same leak after rebuild with FelPro I found the installed seals to be short in circumference not permitting any interference fit at the joint. In other words when the seal halfs were installed in another block and cap torque to spec. the mating ends failed to touch by .006". A new set of seals installed did the trick. Yes just because it is new, name brand and in an unopened package doesen't always mean it is manufactured correctly.

H P Shuttleworth 25130

[Jim T.]

Re: rear main seal - revisited

The GM rear seal #10121044 as per the 2003 GM Performance Parts book is designed to tolerate higher operating temperatures and has more face pressure than other seals for superior leak protection and is used by most NASCAR teams.

[Chuck R.]

Re: rear main seal - revisited

I always rotate the seal so that when the seal halfs mate, they do not create a straight line across along with the main cap.

Chuck