Black stuff (oil?) seeping out of Sky Tech 149 NL starter. Any ideas?

During annual today, I noticed that there where some black stuff seeping out of a flange on the Sky Tech 149 NL starter.
It felt oily beetween the fingertips.

It had spilled on the side of the FI and also made a 30 cm stripe on the lower cowling.

Here's an overwiew of the problem: black stuff on the lower starter-flange and some black stuff on the FI:





Here's a closer look:







Here's the black line on the lower cowl.






It's about 20 hrs since I had the cowl off, and back then, there was no black stuff on the FI or the cowl.

I've done annual on this plane since 2008, and this is the first time I've seen something seeping out of the starter.
The plane now has 304 hrs TT.

Have any of you seen or experienced this before?
Anyone have an idea to what's going on?

Thanks guys.

leak up front?

If you have a CS prop, check the seal and both sides of the Flywheel for oil residue.
A leaking CS seal or main crank seal can migrate into the starter's gear opening and cause oil runs to appear on the bottom of the starter.

I found this on a lightweight starter, not sure how relevant it is to your setup.

Also check the base of the #2 cylinder which sits right above the starter. Any oil leak from here will drip down onto the starter.

++ for what Kurt said. I had the same thing and it was the base of #2 right above the starter.

My guess is a crank seal. The seal may look dry but oil dripping off the starter is a good clue. You may have to remove the prop and flywheel to check it and the seal might be pushed out of the case due to lack of glue. Larry

Starter

Mine looks like that when the starter housing bolts get loose.

Thanks for all the input guys. Highly appreciated!

I didn't think on other sources for the leak other than the starter, so thanks for pointing out other possibilities!
I'll check the things you mention and report back.

The M/T prop is due for the 6 year overhaul by the end of July, so it's going off anyway. Then I'll be able to check for leaks in that area.

BTW: here's another pic: as you can see, there's also some oil on the "mixture reversing bellcrank". (or whatever the correct name of that thing is...)
Guess that is another indication that the oil-leak is somewhere forward of the starter, other than the starter itself? (as long as there's black oil-stains at several places)

Aluminum oxide

Looks like aluminum oxide, like the assembly is not tight and fretting. I know that doesn't explain the oil, but could it be grease from inside the starter?
On mine, the two screws that hold the cover on came loose. I had similar staining but up near the pinion cover. The screws are SAE thread in an aluminum casting...generally this is bad practice. There should be thread inserts in those holes but they don't bother. Anyway mine flew apart shortly after I found the screws loose. It was under warranty and they had told me to just tighten them back up. Shortly after it few apart leaving me stranded.
Tim

problem found

Here's an update: today I took a close look at the areas mentioned in the posts above, but there was clear to me that the dark stuff came from inside the starter.

When I grabbed the aft half of the starter, I could move it ever so slightly in relative to the front half. (this half that is bolted to the egine)

Therefore I took it off the engine, and took it apart along the flange:






The only thing holding it together, where two small bolts. One of them was VERY difficult to remove: it was no way a wrench or a socket with normal thickness would fit since the bolt was VERY close to the starter-body:







Therefore I had to use a small-nosed plier, fiddeling the bolt off:







Inside the starter, I found grease several places:
On a spring and bolt assy:








In a housing:






To me, it looked like the grease had turned thinner in a way, allowing it to seep out of the flange.
Since the aft of the starter was alittle loose from the front half, the flange was not tight. There wasn't any type of sealant beetween the two halves either.

To me, those two small bolts (5 mm?) holding the two halves together, looked VERY small and fragile.
The edge of the two halves had flanges who fitted into eachother, so the torque-forces where absorbed be these formed flanges, but we're talking pretty serious torque here, everytime the starter is engaged.
To me, the construction looked alittle fragile.

Also, I thought it was strange that the starter was bolted to the engine with BOTH startwashers and regular washers on three out of four bolts:



(The starter was installed on the engine by the manufacturer before it was shipped to me)

When you put a regular washer under a starwasher, then the starwasher doesn't have the grab it's supposed to, no??



All this beeing said; it was nice to find to spare share-pins glued to the bottom of the starter:






It was also nice to get a chance to do the procedure necessary if I ever need to change a shear-pin.
It's rather time-consuming, alot of different tools is needed and it's pretty tight space to work in.
Also, the snorkel has to come off to gain access.

I hope I don't have to do this on a small and deserted field during wintertime!

BTW: after seeing how difficult it was to remove one of the small bolts, I grinded down a socket until it fitted on the bolt. Now I can install it and take it off with a socket instead of a pliar...





On Monday, I'll send a mail to Sky Tech asking them about the grease inside the starter. It'd be nice to know what type it shall be, how much and where.

I'll post an update when I get a reply from them.

Awesome post of troubleshooting your starter problem

What a fantasitc step by step post of how to troubleshoot this problem. really great pics and step by step shots. i'll remember this one when I have to do the same thing someday! (Hopefully not in the same horrid conditions you also mentioned)

Threads

Alf, consider how the screws came loose. You'll note they have lock plates, I assume yours still had the plates intact. If so, guess how the screws came loose?
See my post above. I'd try to get a new housing out of them if possible or better a new starter. They're good about taking care of customers. Failing that, I'd investigate putting thread certs in the housing and new screws. Maybe there is a materials guy here that can address using SAE threads in aluminum castings, but in my experience this isn't normally done.
Best luck,
Tim

Update

I've been in contact with Sky Tech now and they said that it probably had been moisture inside the starter.

They said to clean up all grease and moisture from inside the starter, regrease the two gears on the shaft with a very light coat of lithium grease, put it all back together and put it back into service.

The two small bolts have to be torqued to 55 inch/lbs.
Thinking back when I disassembeled it; those two bolts didn't feel like they had 55 on them, it felt less than that.

Tim: the lockplates where intact, so I wonder how the bolts lost their torque? Guess you've a good point in your post above.

Anyway; after the two halves of the starterbody where put together and torqued to spec, the two halves couldn't be moved in relation to eachother, so that was nice!

During ground test afterwards, the 360 fired right up and purred like a kitten as always. No GRRRRR-sound from the starter nor the ring gear either!

So the starter is back in service and I'll keep an eye on it from now on.

Nice write up and photo documentation.
I am similarly affected by the black oily stuff on the starter and had previously questioned Skytech about it and was told it had to have come from an external source. Looks more likely to be liquified grease from inside the starter from your investigation. Not sure I'm buying the moisture story.

ao.frog said:

I've been in contact with Sky Tech now and they said that it probably had been moisture inside the starter.

They said to clean up all grease and moisture from inside the starter, regrease the two gears on the shaft with a very light coat of lithium grease, put it all back together and put it back into service.

The two small bolts have to be torqued to 55 inch/lbs.
Thinking back when I disassembeled it; those two bolts didn't feel like they had 55 on them, it felt less than that.

Tim: the lockplates where intact, so I wonder how the bolts lost their torque? Guess you've a good point in your post above.

Anyway; after the two halves of the starterbody where put together and torqued to spec, the two halves couldn't be moved in relation to eachother, so that was nice!

Click to expand...

If the screws were loose, but had intact lock plates, then either the threads pulled or the height of the assembly changed enough that the screws loosened.
Without having one in front of me to look at its hard to say, but if it were mine and it was out of warranty, I would install some thread inserts.
Like I said, they had me tighten mine up, which I did, and it failed just a few hours later. I would make it an item of close inspection before esch flight for a good long while, especially if flying away from home base.
Tim

Regarding how the bolts came loose, there is nothing wrong with bolts in aluminum, if it is not a highly alloyed version that has no yielding for thread compliance. My guess is from the color, that this is a casting and ok. Millions of motorcycles have threaded fasteners and they always snap when coming out. Very tight. The difference is they have much more stretch length. This application has a short stretch length and any loosening gets accelerated. I would not use a serrated washer under these bolts, it reduces the contact area and is more likely to lose tension than a good, hard washer. Further, a hex/torx type cap screw would be much easier to install and torque, so replacement recommended, unless the ground socket trick worked.

Without going into stories, the bolts should be replaced with new ones, it is very possible one yielded, if so it will again.

Also, blue loctite not the threads would not hurt.

Thanks for a great writeup, I have archived for my repair manual! A clean, oil free cowling allowed this to be caught very quickly before a really expensive repair or dead-on-ramp condition occurred. If it leaks - fix it promptly. I like it!

SAE threads

Thanks Bill I was more referring to the SAE threads into the cast Aluminum. In my experience, it's not often done. What are your thoughts on that?
That was the what failed on mine, the threads pulled and it flew apart.
Tim

Thanks for this, Alf. Your thorough documentation gave me the confidence to buy a 149-NL off a local certified plane for $50 that seemed to have the same issue (condemned by the guy's mechanic, and the shop had one in stock, so it was replaced outright rather than exchanged).

Took it apart and cleaned it up, called Sky-Tec about a couple issues. After a nice talk with a technician, we determined I have a relative antique, but still likely to give more service, and he is sending me some parts to update it, to include the latest and greatest bolts and washers to keep the two castings together.

+1 for Sky-Tec support!