Oil leak, Main seal

Raider2532 · Post by **Raider2532** » Sat Dec 17, 2011 7:02 pm

My M38A1 leaks oil. Its around the bellhouse area. Main seal probably? If so do I have to pull the engine to put in a new main seal?

53a1 · Post by **53a1** » Sat Dec 17, 2011 7:14 pm

I'm rebuilding an F-Head engine over the holidays so I've been reading up on this. Seems there is a lot of controversy about the rear main seal. I'm going with a rope seal and you need to have the crank out to replace the rope seal. If you are going to use a modern lip seal, read the tech bulletin that Wes has posted a million times.

circleburner12 · Post by **circleburner12** » Sat Dec 17, 2011 8:27 pm

53a1, im also in the process of building my f134. i cant make heads or tails out of which seal i need to use. my crank was bad so i found another one and had it turn.

then i found out my block had cracks in the valve seat's. so i found another military block had it machine also. do you know if if may cause a problem using two different components from two difference engine's?

can you tell me what the deal is about the rope or lip seal!. thxsmichael

53a1 · Post by **53a1** » Sat Dec 17, 2011 9:15 pm

What I've read/learned to date...

You can use rope in any F134. You need to read the tech bulletin Wes has posted a million times before using a modern rear main lip seal.

No big deal using another crank/block because the crank is ground to the oversize bearings. Rope seems like a sure thing and worst case leaks a little but will tolerate a wider range of inconsistencies with the seal surface on the crank.

If you are lucky like me and have a local small town machinist that is an engine genius, you should get him to mic everything out/inspect. Every time I go into that place I get an hour of free education.

Cranks can bend, bearing can get spun, things can get screwed up when things crash. Better to check out engine parts when you don't know the history.

Post by **wesk** » Sun Dec 18, 2011 1:10 am

Hello Raider,

I'll answer your question while the thread hijackers are beating to death a very old topic that has been explained to max already!

Both seals can be changed from the bottom with the pan off.

I recommend removing the engine for several reasons.
1-Laying on your back on the floor doing it flat sucks and ends up in a less than perfect job.
2-For either style seal the crank must be loosed and allowed to drop some. If not done properly you can do some real damage that will cost you a lot of additional work.
3-It makes the job easier with the engine upside down on the stand. Plus you get to give everything a thorough once over review. And not mentioned often is the fact that engine oil dripping from the rear end of the oil pan or from the bellhousing can be a rear seal leak or a rear cam journal welsh plug leak.

There two ways to confirm which it is:
1-Remove the engine and inspect behind the flywheel and if that's dry then pull the pan and do the work the right way.
2-Lay on your back, change the oil seal the hard way, discover a few days later it still leaks then play dumb and do it all over again or play smart after being dumb and pull the engine.