Leaking Crankshaft / Flywheel Oil Seal

[Jaffa]

I pressed the seal in so it is hard up against the machined step at the bottom of the recess.

I also seated my seal fully into the case so it bottomed out. Six years later and no leakage from that area. I'm not sure, but I suspect if the seal isn't sufficiently seated, the fillet on the back of the flywheel interferes with the seal.

Not to belabour the obvious, but did you replace the o-ring at the same time you replaced the seal?

Seal, o-ring, pilot bearing, felt seal and 5-hole washer all replaced. Endplay checked and adjusted as well. Also put a smear of hylomar on the seal outer before fitting.

Craig

[Amskeptic]

I pressed the seal in so it is hard up against the machined step at the bottom of the recess.

I also seated my seal fully into the case so it bottomed out. Six years later and no leakage from that area. I'm not sure, but I suspect if the seal isn't sufficiently seated, the fillet on the back of the flywheel interferes with the seal.

Not to belabour the obvious, but did you replace the o-ring at the same time you replaced the seal?

Seal, o-ring, pilot bearing, felt seal and 5-hole washer all replaced. Endplay checked and adjusted as well. Also put a smear of hylomar on the seal outer before fitting.

Craig

Seal leaks have many causes, and we cannot lean on any one potential source as The Cause This Time.

I have installed seals at varying depths to avoid running in an already established groove in the flywheel, I have seen flywheel radius ride when a seal has not been inserted far enough (shiny all the way around the shoulder of the flywheel) and the stupid thing wasn't leaking a drop. It is not a rocket science moment to install a seal, and some have not been exactly equidistant around the circumference, yet they worked fine.

I have found three subtle variances that can maybe increase the potential for leaks.

1) A smooth edge to the crankshaft is critical for a happy o-ring.It needs to be smooth both across the flat end where the flywheel butts to it, and the circumferential edge where the seal has to prevent oil from coming in from the #1 main bearing bath. I am surprised at how many crankshafts show chew marks around here. Likewise, the o-ring groove in the flywheel has to be clean clean clean if the o-ring is going to have a chance. Radial oil marks emanating from the bolts is a good clue the o-ring has not been working.

2) Grease + oil the flywheel's seal riding surface and packing the lip with grease keeps the seal lip cool as it breaks in to the flywheel. If you have ever had rug burn, you know that friction creates heat. We want just enough friction to let the lip edge "relate" to the metal of the flywheel, but we do not want synthetic rubber-melting heat. Radial oil marks up the backside of the flywheel is a good indication of seal contact surface not working.

3) Seal fit in the bore of the crankcase varies widely. An easy palm-push fit means that it will be loose when the engine heats up. In this situation, a sealant is called for, very little required. When I dry fit a tough push seal, I do lubricate at installation with GumOut crab spray. It is slick and easy then evaporates, leaving a snug seal installation. General oil contamination all around the front case area with a dry clutch plate area, dry flywheel bolts, and a little pool of wet oil at the bottom of the seal suggests outer seal failure.

Remember that oil flings round, so be careful with your blame.

In the cases above and many other cases elsewhere, you do not want to over smooth shine surfaces that much relate to each other. A little sanding tooth helps both lubrication and sealant applications.
Colin