Oil leak MT Prop

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dmloftus
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Re: Oil leak MT Prop

Post by dmloftus »

OK thanks
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Re: Oil leak MT Prop

Post by dmloftus »

Rich wrote: Mon Feb 21, 2022 6:20 pm Also, not to be alarmist, but when wiping that streak off, I'd take a careful look and make sure that there isn't a crack in the metal underneath that grease.
Quick update - after R/T from Atlanta to Austin and several short trips since, no additional grease on the prop and fully functional. No cracks or other damage visible. Thanks for the advice.
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Re: Oil leak MT Prop

Post by dmloftus »

Started a new thread, but should have posted here. No grease issues since May 2020. But flew Atlanta to Cincinnati today and noticed this strange spatter on the bonnet when I landed. No obvious leaks under the cowling, belly, etc. Colder temps than I normally fly down south, but still 20F at altitude today. Feels more like oil than grease, and Dave's earlier thread mentioned grease would be yellow. Probably takes just a few drops of oil to cause this pattern in flight. Haven't seen this type of spatter in 2 1/2 years of ownership. Possible sign of prop governor leaking? Safe to fly home?
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Steve
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Re: Oil leak MT Prop

Post by Steve »

David - Grease leaks would be that color as well, but usually originate from the blade seals, and run up the blades due to centrifugal force before spraying back on the cowling and windshield. On your photos, I don't see any splatter on the blade (small visible portion) or the aft spinner, so I would be inclined to think that the leak is most likely oil from the prop O-ring, or less likely, the front crankshaft seal. Removal of the upper and lower cowl and careful inspection should reveal the source.

The prop governor is quite a bit further aft, on the left side of the engine, and leakage there usually drips downward toward the starter.
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Rich
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Re: Oil leak MT Prop

Post by Rich »

Steve wrote: Thu Oct 20, 2022 2:43 am David - Grease leaks would be that color as well, but usually originate from the blade seals, and run up the blades due to centrifugal force before spraying back on the cowling and windshield. On your photos, I don't see any splatter on the blade (small visible portion) or the aft spinner, so I would be inclined to think that the leak is most likely oil from the prop O-ring, or less likely, the front crankshaft seal. Removal of the upper and lower cowl and careful inspection should reveal the source.

The prop governor is quite a bit further aft, on the left side of the engine, and leakage there usually drips downward toward the starter.
Having just removed my prop for overhaul and thus had my memory how it’s mounted, I would concur with the prop o-ring as the culprit. I also dealt with a prop governor leak and it does just run down the engine case inside.

To further explain, the o-ring in question is external to the prop itself. If this is the culprit you will see the oil (and it would be engine oil) coming out from the seam between the base of the prop hub and the front face of the flywheel. It may be present on the spinner backplate. The good news is it’s not wildly expensive to replace, but does require prop R&R, which is a fairly tedious process. Figure a couple of hours labor.
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Re: Oil leak MT Prop

Post by Diamond_Dan »

Great excuse to change your alternator belt if needed.
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Re: Oil leak MT Prop

Post by Rich »

I have no idea why, if it is the prop o-ring, it would decide to fail after a number of years. Unlike the blade seals and other internal prop parts it shouldn't really move against the adjacent parts.

BTW, I found the alternator part in stock at Spruce. Lots of parts are not so available, so this was a welcome exception.
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Re: Oil leak MT Prop

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I believe it was the hub leaking grease again. Last winter I saw a few grease streaks up the blade but nothing on the cowling (prior entries in this thread). I had cleaned off the blades and wiped the hub and I haven't seen it on the blades since. Popping the spinner today was an easy diagnosis. Blade 1 is leaking more grease at the hub, which gets slung onto the inside of the spinner, and centrifugal force seems to spread it backward in streaks inside the spinner until airflow picks it up and splatters it on the top of the cowling. Talked with Brett at MT Propellers in Deland FL, who agreed with the diagnosis. BTW, he is a fantastic resource for any prop questions and responds VERY quickly. I was initially looking for go/no go advice from him. He gave me a very good suggestion. He said to rotate the prop until the front weep hole is at the bottom. If any oil leaks out of the weep hole, it is a leak in the front seal and should not be flown. Luckily for me, the weep hole was dry. So we spray-cleaned the inside of the spinner, and wiped the hubs down again. I will be monitoring the grease leakage much more closely and possibly put the prop in for an early overhaul if it continues. It's interesting that this issue has popped up only in colder weather. Maybe the grease seals contract and and allow more grease leakage? Brett reminded me that MT recommends 1400 hours or 7 years TBO. I've debated the calendar-based 7-year overhaul cycle since my prop has only about 600 hours on it since last overhaul. The plane flies beautifully. Any thoughts?
11.jpeg
#1 blade hub
14.jpeg
Inside spinner
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Re: Oil leak MT Prop

Post by dmloftus »

Reviewed another related thread where Arnaud says he heard from MT Germany:
I'm very surprised with the amounts that were told to you.
For a resealing, I was told me yesterday by MT (in Germany) that this is a very cheap and quick operation.
Despite what were told to me by the local prop shop in France, MT (in Germany) told me that these is absolutely 0 risk to continue flying like this and that the O'Ring will never break, and also the prop is made to operate dry also in case all the grease has gone.
viewtopic.php?t=8524&hilit=mt+prop+overhaul&start=10

Anyone else hear that? The manual states "Continued grease leakage after 20 hours of operation from first leakage requires repair at an authorized service repair facility within 5 operating hours."

Also, has anyone had SL23C performed on their prop (key text follows)?
"In the past a few grease leakage problems occurred on above mentioned aircraft-propeller-engine
combination.
MT – Propeller decided that the propeller hub is modified with stainless steel inserts (A-866-D) to reduce
the friction and the wear on the seal area.
Additionally new blade seals (C-057-78) with increased preload and
MT 2 Propeller Grease with higher viscosity and special additives will be used."
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Re: Oil leak MT Prop

Post by Steve »

My hub had the steel sleeves inserted at the first overhaul (at 12 years, I think). Prior to that it leaked a small amount of grease intermittently, but never as much in the photos. The hub had to be shipped from my shop to Germany for this work - it cannot be done at Service Centers. As I recall, this added about $1K plus $300 shipping to the usual overhaul cost. Not a single speck of grease has leaked since then, including after I had new scimitar blades installed about 80 hours ago.
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