leaking front seal

Witmo

Witmo

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Tim
Noticed a streak of oil on front of cowling and believe it to be from a leaking front seal on a Lycoming O360 with fixed pitch prop. What are the chances of having serious issues if we continue to fly as is for awhile? This is a working towplane (gliders) and now is the start of the best weather for soaring. I don't know if the existing seal is the solid or split version. I suspect we've lost about a quart of oil in the last four hours of operation. Engine has less than 75 hours since MOH.
 
Grease or oil coming out of the blade root likely means it has been over greased and may have blown the seal. Send the prop to the shop and have it re-sealed. In the mean time, I wouldn’t fly it. If it fails, the blades can go flat pitch.
 
Witmo said:
Noticed a streak of oil on front of cowling and believe it to be from a leaking front seal on a Lycoming O360 with fixed pitch prop. What are the chances of having serious issues if we continue to fly as is for awhile? This is a working towplane (gliders) and now is the start of the best weather for soaring. I don't know if the existing seal is the solid or split version. I suspect we've lost about a quart of oil in the last four hours of operation. Engine has less than 75 hours since MOH.
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One relatively easy-to-check cause is a clogged oil breather. If it's plugged it can pressurize the case and force a leak at the seal. As for how long you can run it with a leaking seal, it depends on what's causing it ;)

Nauga,
and the old joke about blowing a seal
 
nauga said:
If your fixed-pitch prop goes to flat you've got bigger problems than a leaking crank seal.

Nauga
cranky
Click to expand...
Missed that part. Thought it was constant speed. Oops
 
I don't know of anything catastrophic that is likely to happen as a result of a leaky front seal. You just need to monitor and top the oil as necessary. That said, is the engine shop which assembled the engine nearby? This should be an easy one day fix if you can get on their schedule. Alternately, the rebuild shop might pay to have a local mechanic fix it if the rebuild shop is a long way away.
 
Witmo said:
Engine has less than 75 hours since MOH.
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FWIW: if your engine is still within its warranty period may want to give the shop a call and get their input before trying any quick fixes that may void it.
 
I doubt you’re towing gliders after dark. Spend a couple hours changing the seal after you’re done for the day, assuming you know for sure that the seal is the culprit.
 
Change the seal. If it's leaking it's either cut or loose. Either way if it comes out or apart it will puke out all your oil in short order...
Then you'll be a glider towing a glider...not really fair to the folks on the other end of the line.

Chris
 
Witmo said:
Noticed a streak of oil on front of cowling and believe it to be from a leaking front seal on a Lycoming O360 with fixed pitch prop. What are the chances of having serious issues if we continue to fly as is for awhile? This is a working towplane (gliders) and now is the start of the best weather for soaring. I don't know if the existing seal is the solid or split version. I suspect we've lost about a quart of oil in the last four hours of operation. Engine has less than 75 hours since MOH.
Click to expand...

I would pull the spinner and verify it is not leaking at the plug in the end of the crankshaft (if applicable) then take a good look at the crankshaft/crankcase seal. I've seen an O-360-A1F6D with a constant speed prop flown for about 45 hours with the seal not adhered to the crankcase but loose and spinning with the crankshaft.

Its really odd tho because I've also read online where some make a large mess http://www.vansairforce.com/community/showthread.php?t=118988&highlight=crankshaft+seal

I think the severity of the situation is dependent on many factors, proper crankcase venting and spinner/cowl design and airflow around the area.

Years ago a 172 with an O-320-D2J landed at my airport with a nearly empty oil sump, the mechanic that inspected the inner diameter of the front crankshaft journal didn't get the plug seated well and it blew out in flight and they almost lost that engine due to oil starvation.

If the plug was leaking there is no way I'd be flying it.

If the crankcase nose seal was loose I wouldn't fly it either.
 
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