"Mark S Conway" wrote in message
news:cgCrb.157136$Tr4.422856@attbi_s03...
What would cause a crank seal to leak?
Seal got replaced, and 15 hrs later, started leaking again.

Any thoughts?

Thanks



I don't know about Lycoming but Continental has an old service letter, iirc,
for lightly sanding the crank where the seal fits with something like 320
grit at about a 30 degree pitch. I've seen it done at 45. Oil is "screwed"
thereby back into the crankcase, as the crank turns. I rebuilt an engine
which had this problem and it leaked copiously around the new seal. The
crank had a little wear and scoring from the old seal, but the tiny "mill"
marks solved the problem. No more leak. This should be done by a pro,
natcherly. And, of course, the pitch must be like your prop's. If it's in
the wrong direction you screw the oil out onto the nose and aggravate the
problem.