1984 Mooney M20K TSIO-360-LB oil leak/loss of oil pressure

[Logwes21]

Hi All,

I purchased a 1984 Mooney M20K within the past 6 months and it has been great. However, I recently had a flight in CA where I took off, climbed and cruised for about 20 min, and then noticed that my oil pressure was beginning to drop. I was about 15 min from the closest airport so I diverted and set up to land. By the time I landed the oil pressure was at 3 psi, but rebounded to about 14 psi once I got on the ground. Taxied over to the closest maintenance facility, popped the cowlings, and discovered that I had lost about 3-4 quarts of oil during the roughly 30 min flight (most of it on the belly pan). Everything in the engine was a little wet as it usually is but there was no distinct leak location. The left side of the bottom cowling seemed to be where most of the oil had collected. My first thought was maybe a push rod seal on cylinder 4 but I’m not sure if it’s capable of pushing out that much oil. Wondering if anyone has had something similar happen or any idea on what the cause/leak location could be. 

Continental TSIO-360-LB with approximately 500 hours SMOH.

Thanks!

 

[rklems]

Push rod tubes are drain back from the oil pushed up in to the top of the head from the hydraulic lifters, there is no real pressure there to have a significant volume leak out, especially in such a short flight. A blocked scavenge port or failed scavenge check valve would cause oil to flood the turbo bearing and be pumped out at fairly high velocity (I’ve seen a Rocket that did this twice and pumped 6qts in about 15m both times… there is actually a service bulletin on coking in the scavenge port on that conversion). But you would get a lot of smoke and of course the exhaust is on the right side, not left. The high pressure oil outlet that feeds the turbo is on the left side so perhaps check that for tightness, as well as the other end of that hose at the inlet check valve. I imagine a good wash down and engine run would probably show where the oil is shooting out pretty quickly  I would of course be concerned with the low oil pressure condition, as well as if you went below the minimum oil level and potentially starved things for oil.

[Ragsf15e]

5 hours ago, Logwes21 said:

Hi All,

I purchased a 1984 Mooney M20K within the past 6 months and it has been great. However, I recently had a flight in CA where I took off, climbed and cruised for about 20 min, and then noticed that my oil pressure was beginning to drop. I was about 15 min from the closest airport so I diverted and set up to land. By the time I landed the oil pressure was at 3 psi, but rebounded to about 14 psi once I got on the ground. Taxied over to the closest maintenance facility, popped the cowlings, and discovered that I had lost about 3-4 quarts of oil during the roughly 30 min flight (most of it on the belly pan). Everything in the engine was a little wet as it usually is but there was no distinct leak location. The left side of the bottom cowling seemed to be where most of the oil had collected. My first thought was maybe a push rod seal on cylinder 4 but I’m not sure if it’s capable of pushing out that much oil. Wondering if anyone has had something similar happen or any idea on what the cause/leak location could be. 

Continental TSIO-360-LB with approximately 500 hours SMOH.

Thanks!

 

I don’t have anything to add, but please let us know what you find!  Ive got an SB engine with 230 hours on it, so im definitely interested.

[rklems]

Loose oil filter, cracked oil cooler, and both turbo check valves and the hoses are also potential sources of high volume oil leaks in that area.

[Z W]

There are many places it could have sprung a leak. I would expect a thorough wash down, followed by a run-up with the cowl off, will let you find it.

Good time to check the date of manufacture on your oil hoses. There are quite a few running to the oil cooler, turbocharger, check valves, and wastegate. They should have been changed with your engine overhaul. Otherwise some recommend changing them every 10 years, but it's an often-missed maintenance item.

[Ragsf15e]

If we’re going for easiest place to look and most often recently “touched”, I’d have a good look at the oil filter.  There are a surprising number of ways to get distracted and not torque it properly.  People make mistakes, it happens.

The other thing that I’ve seen from this forum is that the check valves are very thin aluminum and if the wrong adel clamp is used or it’s badly positioned, you can wear a hole in the check valve.  The higher pressure one would certainly pump out a lot of oil.  I don’t think an internal failure of tge check valve would cause this though?  Someone correct me if im wrong, but an internal failure of a check valve would just lead to the turbo leaking a bit when the engine is off.

edit: there’s even an sb for the adel clamps and a specific type (with yellow fuel/oil resistant cushion) to use for the check valve s.

[Pinecone]

Pushrod tube can push out a LOT of oil.  Even though they are drain back.  On my -SB there was a problem with one O-ring it it pushed out about 2 quarts in 30 minutes.

The best way to find the leak is to clean the engine compartment with mineral spirits.  Then add  1/2 - 1 ounce of florescent dye to the oil.  Run it a couple of minutes and look for the leak with a V light.  It works best if you can get it into the shade or a hangar.