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Maintenance advisory - M20K 231 (mabye 252 also)


jrwilson

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My 84k, 231, with less than 180 SMOH has been a good, reliable plane.  Rarely do I have any oil leaks, and if I notice something small, it gets tightened so no more leaks.  Two flights ago, I noticed a bit of oil on nose gear door so I did some snooping and it looked like it was coming from the turbo check valve.  I talked to the mechanic and he thought it was coming from above there, on the accessory case (Not sure if that is the term, but right above the oil filter) and collecting on the check valve.  He tightened the accessory case and the check valves and off I went.

The next flight, about .4 hours, there was MUCH more oil on the nose gear doors, on the nose gear and all over the check valve/oil filter area (Accessory looked clean).  So I parked it where it was and had a mechanic look at it Monday.  It appears the adel clamps were loose, allowing movement and chaffing on the supply side turbo check valve, under the clamp.  The chaffing causing two tiny pin size holes in the casing of the check valve.  Hot oil squirting all over.  Very little actual oil was lost, pressure and temperature never varied (Probably a couple of tablespoons of oil at most). 

So, 231 owners, check your adel clamps on the turbo check valves and make sure they're snug, there shouldn't be any play for the check valves to move around.  I think there was a SB about Dukes check valves, but I'm pretty sure these are not them.   $500 for a new check valve... 

Edit: I just called Top Gun (MSC) and they said those adel clamps should be inspected and changed every year...

Edited by jrwilson
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Those check valves are bad about wearing through with the Adel clamps. I think I remember reading somewhere that they make two different type Adel clamps. You might do some research. As expensive as the valves are, it is worth some effort.

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7 hours ago, DonMuncy said:

Those check valves are bad about wearing through with the Adel clamps. I think I remember reading somewhere that they make two different type Adel clamps. You might do some research. As expensive as the valves are, it is worth some effort.

I think there was a SB with the dukes valves.  The mechanic put new clamps but yeah I'm going to try to find a way to keep that from happening.   It happened not too far from home so it's not that much of an inconvenience, but had I been on a long trip or somewhere without mx, it would have been a real pain.

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