Oil Leak help needed.

zav6a · #1 11-12-2011, 12:39 PM

Experts

First, 0-320 B2A with constant speed prop.

Has anyone experienced a situation in which it appears that oil is accumulating in the base of the starter? I suspected the main crank seal but when I removed the starter there was an accumulation of oil in the cavity between the starter and the crank case. I looked hard for a case crack but found none. One of the case half bolts daylights in this cavity. I suppose it is possible that oil could leak between the case halves, into the bolt passage then past the threads and finally into this cavity.

The case bolt is along the portion of the case where the pressurized oil for the prop control is housed. And I do have a Whirlwind 151 that uses higher than typical control pressure.

I am asking if any of the folks that have a lot of experience with Lycomings have ever seen such a thing and I hope an easy fix.

Pat Hatch · #2 11-12-2011, 12:59 PM

I was going to ask if you had a constant-speed prop, but I see that you do. I had the identical leak as you describe and after much searching (using a variety of methods), I found the leak to be coming from the base of the 90° AN fitting for the prop control in the nose of the case. I first tried to get another rotation out of the fitting, but when this didn't work, I tried other fittings until I found one that would clock the fitting properly with a good tight fit. Whatever you do, don't over-torque this fitting as it might crack the case and you definitely don't want to do that!

Also, I used fuel lube (EZ Turn) to seal but there are other good sealants for a pipe thread (e.g., Permatex).

[Edit: one of the reasons this kind of leak is so hard to find is that it only leaks in flight when prop governor pressures are highest. I could not get my leak to show up on the ground and that is what is so frustrating about finding it. Running the engine on the ground simply does not get oil pressures up high enough for the leak to show up. You have to load the prop aerodynamically for it to leak. At least that's what I found in my case.]

erich weaver · #3 11-12-2011, 04:10 PM

Yup, same experience, oil accumulating inside starter mount. I have just lived with it up to now, as I haven't been losing much oil, but I'm definitely going to check to see if Pat's solution works for me.

Erich

turbo · #4 11-12-2011, 04:57 PM

pat, nice find. you are like a hound dog. what method did you use to find that kind of leak?

Pat Hatch · #5 11-12-2011, 05:46 PM

Quote:

Originally Posted by turbo

pat, nice find. you are like a hound dog. what method did you use to find that kind of leak?

The method that works the best for me is to use the Magnaflux dye penetrant developer. You can purchase just the developer in a spray can. It looks like a white powdery paint when it goes on. Any oil will leave tracks or streaks in the powder as it flows. So, first you wash down the engine really well, then spray on the developer, cowl up and go fly. After you land you can readily see where any oil has been. Works really well. I have heard others swear by baby powder, but for flight I would think it would blow around too much. The developer sticks and lasts longer. Easy clean up with solvent.

I'll bet you were in Winter Haven today!

rocketbob · #6 11-12-2011, 05:49 PM

Fuel lube doesn't work well as a thread sealant.

Pat Hatch · #7 11-12-2011, 06:05 PM

Quote:

Originally Posted by rocketbob

Fuel lube doesn't work well as a thread sealant.

Bob, yes probably Permatex would be better but for this issue I wanted the lubrication element of fuel lube to torque the fitting. So far it has been perfect over a year after I found this leak and installed the new fitting with fuel lube. If it leaks again (which I doubt), I'll probably try Permatex #2. I think what is more important is to get a good solid snugness of the fitting at the correct clock position.

By the way, some might say run an NPT tap through the case but I would be concerned about filings dropping into the engine. A more reliable solution, I think, is to find the fitting that lines up best. I tried about 3 or four before I found the perfect one.

turbo · #8 11-12-2011, 08:05 PM

[QUOTE
I'll bet you were in Winter Haven today![/quote]

pat, i passed by winter haven and headed up to grass roots airpark for the antique biplane / cub flyin. what a perfect day for flying in florida today. after that kim n i went over to pilot country and borrowed a car to see her son near by. back to stuart by sun down and the airport was back open from day one air show in stuart. putn my plane on display in front of ower EAA booth tomorrow for day two. we need to get together soon. feel like getn up early wednesday for sebring? later.

Pat Hatch · #9 11-12-2011, 08:46 PM

Turbo, I heard Winter Haven was quite active, saw some pix, lots or RV's. I'll call you to discuss Sebring.

rv9aviator · #10 11-25-2011, 12:37 PM

I have an annoying oil leak on my freshly rebuilt 0-320-E3D engine and am not sure how to stop it. I sprayed the engine with developer and it showed up around a through bolt that holds one of the front cylinders on. It is one of the large nuts and seems to be leaking between the nut and washers and the front of the cylinder flange and not at the cylinder base. Is there a sealant I can try behind the nut or will I have to pull the cylinder?