Question for the A&P's.......Lycoming is still slobbering oil

Question for the A&P's.......Lycoming is still slobbering oil

I have a Lycoming O-320 with 200 hrs that had a leaky crank seal. My A&P and I changed it out with a new one, the new seal was installed perfectly over the crank flange with no nicks or tears. He put (I think it was this....) "Plybond" on the outside of the new seal installed it in the engine and let it set in a warm hangar overnight.

The next day (about 20-22 hrs after the repair) I started the engine and flew the plane for approx 2 tenths and landed to inspect the seal. I found a coating of oil on the case and in the alternator belt hub. I pretty sure it wasn't residual since I thoroughly cleaned the parts and the case area while it was apart. Anyway....I wiped most of the oil off again and flew it for about 9 tenths and landed and did not find any more oil than I found the first time.

Will a new seal seep a bit for the first few minutes?
Are there any other possible areas for a leak to develope? The case seam looked perfect.

Thanks in advance!

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Re: Question for the A&P's.......Lycoming is still slobbering oil

Did you polish the crank while you had the old seal out?
I'm not an engine man, but our local engine shops occasionally have a leaky crank seal. They remove the old seal, then disconnect the plug leads, pull all top sparkplugs. Then one person using a piece of very fine emery cloth, or micromesh, will hold it onto the area of the crank where the seal contacts, while another cranks the engine.
Some specialty shops also cadium plate the crank flange (all the area of the crank that is not exposed to engine oil), for protection from the elements. Sometimes this plating just happens to stop at this location where the seal rides. You can still fix it with the above procedure

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Re: Question for the A&P's.......Lycoming is still slobbering oil

I'm not an A&P, but many have experience with oil leaks.

Under or Over tightening can also cause a leak by distorting the sealing surface?  Are you sure the the leak is coming from the case seal or could it be from the forward crank shaft seal? If all the oil hoses and connections are aft of the air flow then having oil forward of the engine should limit the possibilities.  With all the air flow through the cowling stiring up everything its really hard to identify the source of leaks after flying the plane.

my two cents...

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Re: Question for the A&P's.......Lycoming is still slobbering oil

We had the same sort of issue come up on our Club Archer with an O-360. Turned out to be a case halfs were dribbling a bit. This case was one of an engine at TBO and was to be majored soon so it was band aided for a month until major. Might be worth checking though.

my 2 cents

Vin

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Re: Question for the A&P's.......Lycoming is still slobbering oil

I have a C177rg w/Lyco IO360, and yes, it leaks oil.  I've been told it is at the case halfs.  TSMO is 1300 hours, run great, compression is great, etc.
Is there anything that will help, short of a teardown?
Thanks
DS

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Re: Question for the A&P's.......Lycoming is still slobbering oil

Dave,
You can try some sealant on the seam and it might help for a short while.  Other than that, splitting the case halves is the only way to fix it.  If it's not leaking a LOT (i.e. a qt. every 4 hours), I would fly it--many engines over 1000 hrs develop case half weeping.  Is it leaking around the cyl through-bolts by any chance?

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Re: Question for the A&P's.......Lycoming is still slobbering oil

Thanks for your reply.  I've asked about the thru bolts and I've looked myself,, but it appears to be the case halfs.  Leak seems to be worse, about a qt per 2 hours. 
DS

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Re: Question for the A&P's.......Lycoming is still slobbering oil

My engine quit leaking at the crank seal. Oddest thing...I put approx 7 hrs on it after the seal was changed (those hrs also put me due for an oil change) and it still would seep at the new seal. I changed my oil and filter, replentished the engine with Aeroshell 15/50 and took it for a 30-45 min flight, and found that it still had seeped (I always cleaned off the oil after every flight).
I had been planning on flying to Sun-n-fun and was not going to let a little leak stop me. I put 7.5 hrs on the tack (stopping once for fuel) flying to sunny FLA and when I got there there wasn't a trace of oil. I have since put on about 25 hrs and it hasn't leaked a drop. Matter of fact, the oil level has only dropped about 3/4 of a quart on the dipstick in the 32 hrs since the oil change.

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Re: Question for the A&P's.......Lycoming is still slobbering oil

Once the original crankshaft seal breaks free of the engine case it spins with the crankshaft. 
I don't think a lengthy explanation is required to illustrate what happens when an object spinning at several thousand RPM is placed in contact with aluminum for several hours.

Fortunately Lycoming thought of this and offers an oversize crankshaft seal.  It's split seal and is much easier to install- no practical demonstrations of the birthing process and no fishing with dental tools to get a spring seated.

The next question you should be asking is *why* did the crankshaft seal blow out?

Most of the time crankshaft seals pop out because the crankcase is over-pressurized- followed right behind by improper adhesive (RTFM and use the right stuff).
(note to self- apply this reasoning to recent hair loss)

I would check the crank case breather for partial obstruction- There might be a kink in the aluminum tubing or maybe that 20 year old hose is finally due for replacement? <grin>

Best regards,
RH

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Re: Question for the A&P's.......Lycoming is still slobbering oil

I have had a problem with my Mooney M20J IO360. I have now gone through three crankshaft seals (the original, and two new replacements). They have started to leak. My mechanic glued (what glue is best?) the last one in place, but it didn't help. He thinks it is because I fly a fast airplane and fly fast up to the airport and then cut power too quickly. I usually fly full-power for a 1/2 hour commute, and for the last 8 miles lose 3500 feet by first setting manifold pressure to 16" and then nosing down at 180 knotts for a 1000 to 1500 foot descent. When I get to traffic pattern altitude 2 miles away, I level out for a mile which brings me slow enough to put the landing gear down and also full flaps shortly afterwards. I am then 1 mile from the airport at 80 knotts IAS. I cut power virtually all the way and slip down for the landing.

Is the sudden decrease from 24" manifold pressure to 16 causing the crankshaft seal to have blow-by and then start leaking? Or is it the setting from 16" to idle on the final descent?

The articles I have read so far don't deal with this specifically.  Any thoughts?

Thanks,

Jim

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Re: Question for the A&P's.......Lycoming is still slobbering oil

Just seen this...thought you'd all like to know I since have put nearly 275 hours on that new seal and not a speck of oil.

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