O-320 Oil Leak

[rviglierchio]

I've recently developed an oil leak out of the end of the crankshaft behind the prop. Fortunately this is the first leak in this engine with 1700 SMOH. One friend warned that it may indicate a plugged breather and may get much worse very fast. Others have suggested it's just the start of increasing leaks in a motor coming to the end of it's TBO. And others tell me they don't trust an engine that doesn't leak!

What say you engine gurus? Is this seal replaceable or does it come out only when you split the cases?

Thanks for the help.

762BH

[Kent Ashton]

I've recently developed an oil leak out of the end of the crankshaft behind the prop.

It's pretty easy to check if the breather is clear, unless you might have had it ice up. Put some air to the breather hose and see if it come out of the dipstick tube. If the crankshaft seal is bad, there is info out there on how to replace it with a one piece seal. It involves heating the seal in some hot water and stretching it over the prop flange. There are two-piece seals but they're unreliable on a pusher, I hear. I'm sure your friendly A&P can tell you the details. Sorry I don't have the full procedure.

--Kent

[Juan Rivera]

Remove the prop, if the leak is coming from the inside of crankshaft it is the metal plug that seals the end of the crankshaft when you do not have a constant speed prop. It is not hard to replace. Hope it did not start to leak because the area where the seal seats is corroded. I think there is an AD out to have the area inside the crank at the seal end inspected at overhaul.

[Hank Clark]

As it happens, I just installed a crank seal on my o-320. I just went to my local airport and they sold me a single piece seal. It has just one split which is placed at the 2 0'clock position and set in place with some special fuel proof aviation contact cement. Cost was about $40. Installation was simple enough, although the prop was off and it is still a bit awkward reaching in to where the seal is