Rear Main Crankshaft Seal.

[mechjames]

I have to change my transmission this weekend. It blew it's front seal, and I have a lower mileage one I picked up a little while ago.

My rear main seal has been leaking for about 3 years now, and I should have changed the main seal when I did the transmission swap 4 years ago.

Anyway the snow is here and I can't continue driving my SHO.

My parts store can get both of these fel-pro seals in:

The BS40419, which looks like a regular seal and comes with black silicone:

or the BS40647, which is PTFE rubber, and doesn't look like it needs a sealant

Which one is better? I'm leaning towards the PTFE rubber seal. Just pop it in dry, and thats it:

"Seals made with PTFE rubber have a unique “lay-down lip” contact sealing surface that can run on undersize shafts, seal minor shaft imperfections and virtually eliminate shaft wear. They must be installed dry with no pre-lubrication of the sealing lip."

Kind of similar to Ford's repair kit that they made. An improved seal, without the shim.

 

[Anime]

They can say what they want, but a seal installed dry with no lubricant between it and the crank runs the risk of getting worn on first startup and then never being able to seal. Maybe if it already has some sort of dry lube it will work.

I have yet to find a solution that works other than the shim. Even then, there doesn't seem to be a seal that seals as tight and leak-free as the initial factory-installed part.

The problem with the leaking seal isn't that the shaft or block surface is imperfect, but that it's TOO perfect..it's so smooth and slick that the seal is less smooth and can't make even a liquid-tight barrier..or at least that's what the official word on it is.

My guess is this isn't something that is accomplished easily by hand in a garage, and a machine-installed seal, aligned perfectly and done under controlled conditions, is necessary, however unrealistic.

Silicone makes sense, but is a rather sloppy and usually temporary way of accomplishing a seal.

You could try the PTFE seal, see how it works, and report back. If it does indeed offer a tight seal and deal with the issue, that would be great.

I'm about to replace the seal again, and try a better shim this time. If the PTFE seal is the way to go, that would be nice to know.

 

[mechjames]

I'm going to try the PTFE. If I remember right when I priced it out, it's only like $8 more. Any seal will be better then the one I have right now. I go through about a quart every 500km.

 

[Anime]

Anyone try these PTFE seals yet?

I just bought new Timken Viton seals, but if the PTFE does indeed fix the leaks and I don't need to use the shim, that would be good to know.

 

[blacklake]

I have never tried the PTFE seals, but I have some thoughts on the issue.

the manufactures claim about installing the seal without lubricant maybe valid. Firstly PTFE has an extremely low coefficient of friction (for a polymer), having the seal run dry initially may not be a huge factor. In fact if the general consensus is that the shaft is more perfect than the seal is then maybe the seal is designed to "wear in". That is the seal is intended to run dry for a little while to help the surfaces wear together smoothly and form a liquid tight seal.

 

[dkchrist]

Just put a PTFE seal in my ranger. Viton is a decent material with good chemical resistance but very poor wear characteristics. PTFE has better chemical resistance but may not run perfectly dry. I like PTFE because it tends to coat the shaft and make its own wear surface as mentioned above. The only thing to watch for with PTFE is you have to have the installation tool (plastic expander) to slip it over the crank with damaging the seal.

 

[Anime]

Hm, if PTFE wears that much better than Viton, that makes me think I'd rather have the PTFE seal.

What brand of seal did you use, and does it come with the plastic expander install tool?

You didn't use a sleeve on the crank surface and no oil leaks so far?

 

[boominXplorer]

I have had 3x success rate in a SOHC with the more expensive Fel Pro PTFE seal. It comes with a installer that helps it slide onto the crankshaft, really nice. I have pulled an engine out with the cheaper Fel Pro one and sleeve and it was leaking. I replaced with the PTFE seal and no leak after.