FJ40 Rear main seal leak

[mrtodds77]

I am in the process of converting my 68 FJ40 into a 4 speed. I took it all apart and find a lot of oil in the clutch area. I had noticed the clutch was slipping a lot more.

From what I can tell the leak is either from the rear main seal or through the flywheel bolts. I will post the pictures so you can analyze and confirm.

I see some oil lines coming from one of the flywheel bolts. Is this a common area that leaks? I put on a new clutch and all about 3 years ago.
Do I need to use some kind of thread locker and sealant in the flywheel bolt holes?

Also, there is a flywheel alignment stud piece at the top between the bolts. This seems to be loose. I would think I should use thread locker and sealant on that too? Can anyone confirm? I find it very poor design for these bolts to be open into the main oil chamber of the engine. There is no reason for this and it is a big risk. Has anyone ever built a cover for this?

Also when I look at the flywheel plate it looks like loose stud piece has slightly pushed up metal of the hole it sits in and may be causing the main seal to leak.

Does anyone think that is the real issue here? Is there a way to fix this? Or do I need a whole new crankshaft?

The pressure plate looks ok. But the clutch is toast.

Any pointers would be appreciated. I don’t want to put it all back together to have it leak again.

 

[1FastBimmer]

The flywheel bolts are in blind holes. Looks like someone hit that alignment stud with a hammer and wallered out the hole? It doesn't look like the seal is leaking that bad, could be weeping from the pan gasket as well. Im not sure how proud the end of the crank is from the lip of the seal but you may be able to pull the seal and clean up the crank with some emory cloth or light sand paper if it really is tearing up the seals.

 

[Godfather90]

The flywheel bolts are in blind holes. Looks like someone hit that alignment stud with a hammer and wallered out the hole? It doesn't look like the seal is leaking that bad, could be weeping from the pan gasket as well. Im not sure how proud the end of the crank is from the lip of the seal but you may be able to pull the seal and clean up the crank with some emory cloth or light sand paper if it really is tearing up the seals.

From that picture he provided it does not look like the holes are in fact blind.

 

[mrtodds77]

I have a few more pictures after I took off my bell housing. Some minor oil under the bell housing. I still think my leak is coming from either the flywheel bolts, the rear main seal, or the oil pan seepage.

Is there a bell housing gasket or can I make one with sealant? I don’t see any leaks though the rear oil seals or freeze plugs.

 

[1FastBimmer]

I guess I was mistaken, those holes arent blind. I would pull that rear main seal next and inspect the crank where it rides, if you are leaking oil through the bolt holes only its an easy fix. Not sure why you would want to seal the bell housing to block though?

 

[mrtodds77]

I guess I was mistaken, those holes arent blind. I would pull that rear main seal next and inspect the crank where it rides, if you are leaking oil through the bolt holes only its an easy fix. Not sure why you would want to seal the bell housing to block though?

Well if I seal the bell housing and if I get any oil leak from above like the valve cover it will drip down around the bell housing and onto the ground and not into the flywheel and clutch. Does that make sense?

 

[1FastBimmer]

Well if I seal the bell housing and if I get any oil leak from above like the valve cover it will drip down around the bell housing and onto the ground and not into the flywheel and clutch. Does that make sense?

The bellhousing and block are both machined flat, it would have to be one hell of a valve cover leak to get on the pressure plate and clutch disc. Tackle the major leaks now that you have it apart and don't worry, it will never be leak free like a modern engine. As long as you arent soaking the clutch in oil I dont see the problem.

 

[73FJ40]

It looks to me like the flywheel was loose at some point, the locating pin was centrifugally forced outward radially, noticeably distorting the rear main seal surface with a "bump."

If so, the life expectancy of the seal will suffer.

Were the flywheel bolts held in place with lock plates?

 

[mrtodds77]

Yes, I torqued out the flywheel bolts and had the lock plates on them. I did not use blue lock tite on them because I thought that was overkill. But in hindsight I think the lock tite keeps the oil from coming through the bolt holes.

I was able to use some Emory cloth and tried to tap down the bump a little at it looks much better. I am still not sure if I should do more? Also I am concerned about putting that locating pin back in. With it loose it may start to vibrate again and do get same thing. I am thinking about putting it in with some kind of Epoxy. I don’t know why it is loose anyway? Seems like it should be part of the flywheel and welded in place?

Here is what it looks like after I clean it up.

 

[mrtodds77]

Poser/ Pinhead any advise?