Tips on Replacing Rear Main Seal
Thread Starter
Racer
Joined: Sep 2004
Posts: 424
Likes: 2
Tips on Replacing Rear Main Seal
I started out building my 383 with a bad block, ended up purchasing a short block from Midwest Motorsports. I went in for back surgery the day after the engine was delivered, I put the engine on the stand and it sat for around 7-8 months before I got back to it. During assembly I wound up rotating the assembly alot, checking rod to cam clearances, installing and indexing a mech. roller cam, push rod legnth, rocker arm clearances, valve spring bind,piston to valve clearances, oil pan clearances, ect. Any way right after break-in I developed a severe oil leak which I traced to the rear main seal. I read that excessive rotation on a dry seal can cause this, and since the block sat so long and I did rotate it alot (oiling the cylenders & bearings) I accept that this could be the reason. I have never had a rear main seal problem before, so I want to do everything right. Tips on removal/installation, sealants, ect. will be greatly appreciated. I am using a Felpro dual lip seal & one peice oil pan gasket. Thanks
Thread Starter
Racer
Joined: Sep 2004
Posts: 424
Likes: 2
Originally Posted by BerniesVette
Jimmy, if it is a one piece rear main seal you will have to pull the engine. If it is a two piece rear main seal, you can change it in the car.
Bernie
Bernie
Melting Slicks
Joined: Aug 2003
Posts: 2,135
Likes: 2
From: Dayton Oh
Just a couple of tips as follows for a two piece seal:
1) make sure you face the "lip" of the seal in the correct direction. I believe it should be towards the front but I really can't remember just now (bad hangover today).
2) do not flush up the seal halfs with the engine surface. Instead rotate the seal such that approx. 1/4" is below the surfaces.
3) put a dab of Permatex on each end of the seal halfs.
1) make sure you face the "lip" of the seal in the correct direction. I believe it should be towards the front but I really can't remember just now (bad hangover today).
2) do not flush up the seal halfs with the engine surface. Instead rotate the seal such that approx. 1/4" is below the surfaces.
3) put a dab of Permatex on each end of the seal halfs.
Thread Starter
Racer
Joined: Sep 2004
Posts: 424
Likes: 2
Originally Posted by marshrat99
Just a couple of tips as follows for a two piece seal:
1) make sure you face the "lip" of the seal in the correct direction. I believe it should be towards the front but I really can't remember just now (bad hangover today).
2) do not flush up the seal halfs with the engine surface. Instead rotate the seal such that approx. 1/4" is below the surfaces.
3) put a dab of Permatex on each end of the seal halfs.
1) make sure you face the "lip" of the seal in the correct direction. I believe it should be towards the front but I really can't remember just now (bad hangover today).
2) do not flush up the seal halfs with the engine surface. Instead rotate the seal such that approx. 1/4" is below the surfaces.
3) put a dab of Permatex on each end of the seal halfs.
Melting Slicks
Joined: Mar 2005
Posts: 2,095
Likes: 299
From: Midlothian VA
FYI:
I had a similar issue with a leak at the rear of the motor.
Made the exact same determination - it looked for all the world like the rear main seal was damaged.
Pulled the pan and found that it was only the pan gasket where it seals to the rear main/block area. The oil was leaking through/past the pan bolt right next to the rear seal so there was no good way to tell what was leaking until I pulled it.
Replaced the pan gasket with the one-piece unit and viola!-no leak.
But while you're in that far the rear main is not that much more work.
Point is, the one piece pan gasket unit is the only way to go.
I had a similar issue with a leak at the rear of the motor.
Made the exact same determination - it looked for all the world like the rear main seal was damaged.
Pulled the pan and found that it was only the pan gasket where it seals to the rear main/block area. The oil was leaking through/past the pan bolt right next to the rear seal so there was no good way to tell what was leaking until I pulled it.
Replaced the pan gasket with the one-piece unit and viola!-no leak.
But while you're in that far the rear main is not that much more work.
Point is, the one piece pan gasket unit is the only way to go.
Racer
Joined: Apr 2005
Posts: 494
Likes: 0
From: Virginia
Put a little RTV on the cap, right next to the seal when reinstalling it. There are two small square areas. Saw this tip in one of my books.
Replaced my bolts with ARP studs while the pan was down. Since it hasn't been started yet, can't recommend doing this. Good Luck.
Replaced my bolts with ARP studs while the pan was down. Since it hasn't been started yet, can't recommend doing this. Good Luck.
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Melting Slicks
Joined: Oct 2004
Posts: 2,662
Likes: 8
From: Knoxville Tennessee
Jimmy,
Drop the idler arm so you can remove the oil pan, then remove the oil pump and rear bearing support. With the tranny in it is a tight fit but you can change the seal. Drive the old seal out of the block using a long slender punch being careful not to nick the block surfaces and do the same with the seal half in the support you removed. Once you get the seal moving you can grab it with a pair of pliers and pull it as well to get it out. Installing it is just the reverse. Lube the seal and surface to make it slide around the crank easier and I use a slender piece of hardwood to push the seal around. I installed mine so that the halves stop exactly where the mating surfaces go together but you can install it the way described above. I used a small dab of gray permatex to the seal ends making sure not to get any excess on anything else. I know people who swear by either method and using and not using permatex, so pick which way you want to do yours. Just take your time be careful and you should wind up with a seal that doesn't leak. I hope this helps.
Bernie
Drop the idler arm so you can remove the oil pan, then remove the oil pump and rear bearing support. With the tranny in it is a tight fit but you can change the seal. Drive the old seal out of the block using a long slender punch being careful not to nick the block surfaces and do the same with the seal half in the support you removed. Once you get the seal moving you can grab it with a pair of pliers and pull it as well to get it out. Installing it is just the reverse. Lube the seal and surface to make it slide around the crank easier and I use a slender piece of hardwood to push the seal around. I installed mine so that the halves stop exactly where the mating surfaces go together but you can install it the way described above. I used a small dab of gray permatex to the seal ends making sure not to get any excess on anything else. I know people who swear by either method and using and not using permatex, so pick which way you want to do yours. Just take your time be careful and you should wind up with a seal that doesn't leak. I hope this helps.
Bernie
Thread Starter
Racer
Joined: Sep 2004
Posts: 424
Likes: 2
Thanks everyone for the help, I took the oil pan down last night and the pan gasket was wasted. I was then able to get a closer look at the part of the crank behind the rear main seal, it was dry. I replaced the pan gasket with a Felpro one piece, No Leaks. I'm real glad, the thought of replacing the rear main seal on a new engine made me nervous.