Oil leak vs Grease leak MT prop ?

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Re: Oil leak vs Grease leak MT prop ?

Post by Rich »

Steve wrote:
Mon Jan 25, 2021 3:37 am
Well, I don't think you will need new blades, so the only parts they would need would be the hub overhaul kit, which most shops that overhaul MT props have in stock. What time estimate did they give you when you asked them to work on it?
I believe an actual overhaul also involves some blade work, which can be done at some prop shops:
-Replacement of the erosion shield
-Paint repair (typically the backside black paint is all chipped up.
-Repairs to minor damage at the wingtips.
-There is also a test procedure to validate the integrity of the wood core. *
-Inspection to ensuring no damage/excessive wear to the blade ferrules. *

* Failure of either of these means work that must be done in Germany. In my experience that adds months to the turnaround.

Way back when (2004?) there was actually a recall on the hub itself. Ours was replaced at the time under warranty. If somehow this is one of the old style hubs (it looks odd) this would also need replacement.
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Oil leak vs Grease leak MT prop ?

Post by yl472401 »

Precisely! It is the 183-59B P25NE. I wasn't pay much attention until last night when I was checking out the prop pictures.
There was a date specifies 04/16, which I'm not sure if it is for the manufacture date or not.
I'll def study the log book once I get hold of it and see if this one is a replacement.


Steve wrote:
Fri Dec 18, 2020 12:00 am
Bryan:

The first photo wins the prize. To me, it appears that the source of oil/grease spatter is the small hole at 7 O'clock on the face of the hub. The older versions of the MTV-12 hub (like mine) do not have this hole. MT added it to try to mitigate the grease spatter issue on these props. There was even a service bulletin to drill a hole in the hub of the older S/Ns to try to reduce the spatter. The fix was actually to bore out the hub, and install steel sleeves for the blades, which seemed to allow for better sealing. I had this done when my prop was overhauled about 7 years ago (hub had to be shipped to Germany for this), and it has been dry as a bone since.

The other unusual thing (to me) in your photos, is the gray silicone? around the base of the blades. My blade roots don't have anything like that:

IMG_4339.jpg

although my blades are 180-17f and I suspect you have the scimitar prop with 183-59b blades. The design of the blade root appears much different, but that sealant doesn't look like a factory job...

Your blades do look like they have a very small amount of grease leakage, but I think the majority of leakage is coming from the previously mentioned hole, and running/being blown aft. Now, as to what is causing it, I think that determination will have to be made by a prop shop. Keep us informed as to what you find.

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Re: Oil leak vs Grease leak MT prop ?

Post by yl472401 »

Rich wrote:
Davestation wrote:
Sat Dec 19, 2020 5:14 am
There is next to zero chance it’s oil. The crank flange is well aft of the cowling opening and the air flows rearward from there. It will surely be grease from one of the blade roots, cause for a prop reseal.
Bryan's pictures show little evidence of leakage out of the blade seals. I've had several bouts of grease-slinging and it has always been apparent on the blades themselves. And it didn't look like this. More like a bunch of little black dots with very localized smearing. This is a prodigious amount of stuff.

The seam between the hub and the front face of the flywheel is about 1.5" behind the front edge of the cowl. With the position of the spinner and cowl I suspect that that area inside the cowl is probably dead air, allowing oil that would hit the inside of the upper cowl to drip down to the front edge. With the air flowing across that small gap between the spinner and cowl, there should be a low-pressure area that would draw the oil collecting on the lip of the upper cowl up and out the top to be blown back. Yes, this is conjecture. How to check it out? Remove the upper cowl and inspect the hub/flywheel interface and inside of the cowl, both above and below. Confirmed or eliminated.

The other route for engine oil to find its way out the propeller involves failure of the internal seal that keeps engine oil from getting to the innards of the prop hub. This seal travels with the activating piston and is inside the hub itself. That bit of a smear from the vent hole that Steve pointed out would be an exit point, allowing the stuff to flow back along the inner surface of the spinner. The picture doesn't show much in this area but it's a possibility. From the MT manual:
MT Piston Seal.jpg
Any route for grease or oil that's from within the prop hub itself would show up on the inside of the spinner.

Bryan, Yous should examine the inside of the spinner for any oil or slung grease deposited there. Also remove the top cowing and see if there is any sign of oil coming out of the hub/flywheel interface area and on the inside surfaces of the cowling halves and cooling intake air ducts.
Rich,
Thanks for the diagram. After a refreshment of the knowledge I obtained more than two decades ago, I was able to understand the basic structure of the prop blade. The inside piston was pushed by the oil pressure against the spring mounted at the front end and the seal is essential to prevent oil leak into the inner core of the hub that holds the prop blades. I believe that’s what happened from the engineer works at the local shop through the talk the other today. They have to drain and dry the oil that got into the blades.


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Re: Oil leak vs Grease leak MT prop ?

Post by yl472401 »

Rich wrote:
Steve wrote:
Mon Jan 25, 2021 3:37 am
Well, I don't think you will need new blades, so the only parts they would need would be the hub overhaul kit, which most shops that overhaul MT props have in stock. What time estimate did they give you when you asked them to work on it?
I believe an actual overhaul also involves some blade work, which can be done at some prop shops:
-Replacement of the erosion shield
-Paint repair (typically the backside black paint is all chipped up.
-Repairs to minor damage at the wingtips.
-There is also a test procedure to validate the integrity of the wood core. *
-Inspection to ensuring no damage/excessive wear to the blade ferrules. *

* Failure of either of these means work that must be done in Germany. In my experience that adds months to the turnaround.

Way back when (2004?) there was actually a recall on the hub itself. Ours was replaced at the time under warranty. If somehow this is one of the old style hubs (it looks odd) this would also need replacement.
Prop eventually went through overhaul at a reputable prop shop in Ohio. Here are some pictures took before it was installed back on.Image
Image
Image
Image
Image


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Re: Oil leak vs Grease leak MT prop ?

Post by Steve »

Bryan: Glad to hear that your prop is back! Looking at your photos, I noticed a couple things: your prop doesn't have the front spinner backing plate installed, and the cap screws on the hub aren't safety wired. Every time my prop has been overhauled (twice now) it came back from the shop fully assembled. Also, a number of other things were done as part of the overhaul (painting blades and backing plates, removal of all of the old stickers and application of new ones with the date of OH, static balance, etc.). You can see what mine looked like in the photos I posted to this thread on 21 January.

I am wondering - did you have an Overhaul, or just a re-seal? not trying to make you nervous, just curious...

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Re: Oil leak vs Grease leak MT prop ?

Post by yl472401 »

Steve wrote:Bryan: Glad to hear that your prop is back! Looking at your photos, I noticed a couple things: your prop doesn't have the front spinner backing plate installed, and the cap screws on the hub aren't safety wired. Every time my prop has been overhauled (twice now) it came back from the shop fully assembled. Also, a number of other things were done as part of the overhaul (painting blades and backing plates, removal of all of the old stickers and application of new ones with the date of OH, static balance, etc.). You can see what mine looked like in the photos I posted to this thread on 21 January.

I am wondering - did you have an Overhaul, or just a re-seal? not trying to make you nervous, just curious...

Steve
It was a re-seal.


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Re: Oil leak vs Grease leak MT prop ?

Post by jwx96 »

I had my MTV-12-B/180-17 prop overhauled at 1812 hrs in February 2021 by a MT authorized service center in Minnesota. The prop wasn't having any problems, but it was 6 years after the last overhaul. At about 35 hrs after the new overhaul I began to notice some grease on the cowling. The amount seemed to lessen with subsequent flights but the spattering continued. At 55 hrs I called the prop shop and they asked me to remove the spinner and take some photos, clean off the grease and fly for a few hours to see if it was still leaking, or if the previously leaked grease was just continuing to come out to the cowling. Here are the photos. Each of the blade roots had about the same amount of grease showing. I cleaned it up today and will fly again soon. Is this normal after an overhaul? If not, what should I be expecting the prop shop to do? Image
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Re: Oil leak vs Grease leak MT prop ?

Post by jwx96 »

Follow-up. The grease leak got worse, rather than going away, but then stabilized. It was definitely grease and not oil. The prop shop wanted me to keep flying it to see if it would go away eventually. I think they were hoping it was just packing grease working it's way out. I got to 60 hrs post prop overhaul and contacted the prop shop again. They suggested flying it for another 20 hrs. I had my mechanic look at it and she called the prop shop and then repeated their advice. I started a Savvy ticked ( I use the consulting service, not the full management). They thought the prop should go back, but thought it was ok to wait the extra 20 hrs. I called a Diamond service center and they also thought my prop should go back. They used to have MTV-12-B's on their DA40's and didn't have leaks after sending them to MT in FL for overhauls, but they switched to the 2 -blade metal Hartzell's because of longevity issues. He said they couldn't get 600 hrs from the MT props because the bearings wore out. I flew the extra 20 hrs and then the prop shop asked to take the prop back for an inspection. They found a scored piston bore and complied with MT service letter 18 rev 1, which essentially replaces the piston and places a new ring and seal to prevent scoring in the future. The wear was allowing the cylinder pressure to pressure the grease contributing to the leak. Hopefully this will take care of it.
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