Front engine bearing seal leaking oil.

[Dwaldvogel]

I have a 1962 M20C with 500 hours since an overhaul on the O-360. I replaced the front seal when the prop was off for overhaul because it appeared as if it was seeping. After approximately 40 hours I noticed oil on the top off the cowling so we replaced the seal again as it was again seeping. 30 hours later and the same thing. My A & P thinks it may be a bad bearing which is wobbling & breaking the seal or possibly just a bad batch of seals. The oil pressure is fine.

Has anybody experienced the same issue?

[MB65E]

I just replaced the nose seal again on our E last week. Same swirly oil pattern on the top of the cowl, top of the Doghouse a mess too. 50 hr SMOH. It's really hard to tell where the oil comes from with the old cowl designe.

The good news is the oil leakage is about half of what it was, but the bad part is I think it's coming out the prop hub blade roots. Ugggg.

Is the face of the prop wet? Fine mist on the windscreen? I don't think you engine bearing is wobbling. The seal does not touch the engine bearing. The seal only touches the case and the crank.

I just flew it 5 hours, and have the mist again on the wind screen.

I'll post a pic of the face of the prop.

Time to PM Cody again...

-Matt

[47U]

One piece nose seal or split type? Is the case cleaned perfectly so the glue bonds well? Is he using the pliobond or RTV? Are you sure it's the nose seal leaking and not the prop o-ring? Is the o-ring changed when the prop is pulled? Has the case been meticuously inspected for cracks or a leak at the split line? I think there's a Lyc service bulletin on nose seal replacement you might google up.

I'd think the mechanic would have some motivation to get this figured out. No one I know likes safetying prop bolts over and over.

[MB65E]

For me- One piece, cleaned extra well with picks, Mek, and q-tips. Pliobond is no longer available in California. Multiple engine shops recommended PRC or 1300L. I used PRC b1/2. New prop oring always. It's a .10 crank, but the SB for the cad plating was done last year on the crank at AIrcraft Specialities. Trust me, I don't want to pull it again either. I'm the one that gets the pleasure. Lol.

I just want to confirm a few oil spray patterns before I start looking for a prop solution.

For those that their crank seal was the cause, was the face of the prop wet too? It's funny watching oil flow fwd at 160kts!

Any thoughts are helpful.

Thanks!

-Matt

[Hank]

Matt--

 

If you have the original guppy mouth without a closure kit, there is reverse airflow out the front of the cowling due to poor pre-computer design. The oil is not necessarily coming from the prop or the main bearing, it could be coming from almost anywhere under the cowling.

 

Clean the engine thoroughly, run it on the ground for several minutes and look for the origin of the oil. Don't forget it could be coming from the accessories at the back of the engine, especially if it's all over the doghouse, too.

 

Just my .02

[scottfromiowa]

I replaced two prop seals only to learn case half separation oil on windscreen and on front lip of cowl...

Good luck

[N601RX]

Pliobond can be ordered from mcmaster Carr. There have been some cases where the seal bore and bearing bore are not machined concentric to each other.

[MB65E]

Thanks guys! Last thing I want is to overhaul the prop let alone change another crank seal due to a leak at the acc case... I'll start looking again.

-Matt

[Guest]

A leaking crankshaft seal can be caused by a crankshaft with too little end play between the slinger and the case. Other causes are improper seal installation, did the installer lubricate the inner surface of the seal while installing it? Other cause can be a cracked crankshaft, but rare unless there is an undocumented prop strike.

Clarence

[Dwaldvogel]

Thanks for all the input guys! I think I'll replace the crank seal and the prop o-ring again but take extra care cleaning everything & re-installing.

I'm always interested in more input if anyone has some.

[MB65E]

Thanks for the input Clarence.  Good point, The end play measured within limits during assembly. Slight forward and aft movement can be felt by pushing and pulling on the prop.   

This iteration of crank seal replacement didn't have too much oil on the crank itself, but had a good amount of sealant around the case and was super clean.  I've changed about 6 nose seals on other lyc's with out issues.    In my picture it was after about 2 hrs of flying.  Fine spray down the face of the blades.  I think the prop has had it.  Also tried I the 2100rpm cruise the other day and couldn't get it to come down below 2300 rpm.  Its probably leaking internally.  I'd hate to put a reworked/ fresh prop on and have it do the same thing.

 

Funny how as I make the airplane better, something I haven't touch needs work.

Thanks,

Matt

 

http://mooneyspace.com/gallery/image/35581-/

[jetdriven]

Thanks for all the input guys! I think I'll replace the crank seal and the prop o-ring again but take extra care cleaning everything & re-installing.

I'm always interested in more input if anyone has some.

I didn't see it mentioned but lycoming makes a 1 and a 2-piece seal. He's the 1-piece seal up in hot water and grease it really good, then install it. Rumor is it doesn't leak as readily as the 2-piece version.

Anyways, as Clarence says, a good installation is key.

[MB65E]

Split seal or solid right? Didn't know there was a 2 piece. 1 piece solid seal is what I installed.

-Matt

[pinerunner]

One other thought. I don't remember where I read it but the crankcase seal isn't meant to resist a great deal of pressure. If there were a restriction in the crankcase vent the natural blow-by (past the pistons)  would slowly pressurize the crankcase and cause oil to ooze past the seal.  Checking for that and cleaning the vent would be easier and cheaper than replacing the seal a bunch of times.

[Lionudakis]

Based on the picture of the blade I'd say the prop needs looking at.

[pinerunner]

Please let us know how it turns out.

[Dwaldvogel]

Thanks again for continued input. I'm pulling the prop tomorrow, cleaning the crank case vent, and replacing the prop seal.