Main seals
Thread Starter
Instructor
Joined: Apr 2002
Posts: 154
Likes: 0
From: Millbury MA
Main seals
I was told that I should replace the main seals in my 79. I get a rapping sound for about a minute or so when I first start the engine(cold). The person that listened to it used a stetiscope and said the noise was coming from the bottom of the engine. His explanation was that the oil is draining out of the bearing due to a bad seal. I have read several threads regarding peplacing the rear main seal. What else shoud I do while Ihave the oil pan off?
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Well, it's hard to diagnose bearing problems without removing the caps, but there are three things to think about at that rear main cap. Oil pump, rear main seal, and rear main bearing. It's possible some sound from the transmission input shaft may have made it through to where he was listening but it's probably one of the first three things.
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Now there is a load of crap. I would find someone who knew something about motors before taking it to this guy again. There is no seal that holds oil in the bearings. He has no idea what is wrong if this is what he thinks.
The rear main seal just holds oil in the pan. It would have nothing to do with a rap at startup. You might have some worn bearings due to mileage and once the oil pressure comes up the clearance is taken up by the oil. Many a car has been driven thousands of miles like this. If it is bad enough though it could cause some bearing or crank or rod damage. The only way to find out is to remove the pan and have a look at the bearings.
Last edited by Gordonm; Nov 5, 2007 at 12:02 PM.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
As noted, it's hard to do remote diagnosis on this stuff, but if it's a real knock vs. lifter noise then I'd be looking to the rod/main bearings.Have a real mechanic look at it
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
