Varying Oil Consumption

[Pinecone]

M20K 252, Encore converted, TSIO-360-SB.

Did a 6.9 hour flight last Thursday to Fort Worth PPP, burned 2 quarts.  This was after a few short flights after an oil change.  Cruise was 14,000.

Normally goes 15 hours on first quart after an oil change.

Did two training flights of 1.8 and 2.0 at low (under 5000), burned NO oil.

I haven't checked the oil since the flight back (7.0 at 17,000).  I can't get an accurate read right after running.  I will go out to airport later to check.

Any thoughts?

I talked to Paul Koropates at the PPP and have one possible reason.  But not a cheap one.

 

[PT20J]

Only two places it can go: out the breather or into the combustion chamber(s). Out the breather could be pressurizing the crankcase by blownby. Burning it would mean it’s getting past the valve guides or past the rings. Since this seems to have come on suddenly, something must have changed. I’d start with a careful examination of the cylinders. 

Sigh, with an airplane, it’s always something. Hope it’s something simple. 

[Pinecone]

But strange that it only seems to occur on high altitude flights.

[MikeOH]

1 hour ago, Pinecone said:

But strange that it only seems to occur on high altitude flights.

If I'm following your OP, you have a sample size of ONE; at least wait until you measure how much oil was consumed on the return flight before you conclude it only happens at altitude.

[Will.iam]

If at altitude then it’s somewhere In the turbo as low altitude the turbo is not working very hard compared to in the teens on up  i would look there first. 

[Ragsf15e]

Can’t some blockage in the breather make the crankcase pressurize at altitude?  Im maybe not remembering that right but I thought there’s a specific blockage that can do this.

[MikeOH]

15 minutes ago, Ragsf15e said:

Can’t some blockage in the breather make the crankcase pressurize at altitude?  Im maybe not remembering that right but I thought there’s a specific blockage that can do this.

I've heard of possible freezing of the breather tube...my vague recollection is that's the purpose of the 'whistle stop' cut in the tube: to provide a vent if the end of the tube in the slipstream freezes closed.  I'd think you'd have to be in pretty solid IMC...but maybe the moisture in the escaping gases is sufficient if below freezing??

[Z W]

I always get varying oil levels after oil changes.  You put 8 quarts in, let it sit, it will measure 8 quarts.  After the first flight, it drops to 6.5 or 7 quarts.  I've always figured it's refilling the filter and all the places oil can splash while the engine is running, and maybe blowing some of the 8 quarts out.  Oil loss seems a little higher if I refill to 8, so I run between 6 and 7.  It now loses/burns a quart every 10 hours or so.

It used to not like to hold anything over 6 quarts and would blow out a lot more.  Cleaning the air/oil separator and changing the gasket on the oil filler cap seemed to help that problem.

I would probably do a few more short flights and monitor the levels and try refilling and seeing if that affects your loss rates.  And a new oil filler cap gasket is cheap and easy if you haven't replaced it.

Old thread here:

 

[Pinecone]

No oil on the belly.

After the oil change there was a ground run to check for leaks, then 3 short (half hour) flights.  My engine has been OK with 8 quarts previously.

Yes, suspect something possibly with turbo.  I talked to Main Turbo Supply and they suggested a couple of things to check, one being the oil scavenge pump.  Also waste gate for leaking.

[Fix]

My TSIO-360-SB2 takes around 2-3 days after a flight before I can read the correct oil level.

Last Oil/Filter change I filled with 7.5qt, and now it reads little above 6.5qt after some couple of hours of flight.



 

[pkellercfii]

I've observed this issue as well, albeit not as severely, with the TSIO-360-MB which powers my Mooney, which is pretty much a non-Encore factory vanilla 252. The highest oil consumption I've ever observed was about a quart in a relatively short flight of about an hour. The oil simply disappears, not being left on the belly, and not visibly coming out of the exhaust or anywhere else. The issue began when the engine was around 500 hours SMOH. It's now just beyond 1100 hours SMOH, and hasn't worsened, in spite of my doing nothing about it, other than keeping an eye on it. I have to observe that my oil operational practice is different from yours. Given that five quarts of oil is the minimum specified for dispatch in the POH, I rarely have much more than six quarts of oil in the oil pan. My current average oil consumption is around one quart every 10 hours. I've discussed this issue with my current IA, and his thinking is that the issue with oil disappearing is that it's probably due to valve guide issues. Unfortunately, that's a relatively common problem with Continental engines with Continental cylinders. My cylinders are Continentals, which were new with the major overhaul, which was under my ownership. Unfortunately as well, doing much of anything about valve guides involves pulling cylinders, which, yes, is expensive, invasive and risky. That's why I've chosen to simply watch and wait and spend the money on adding a quart of oil every ten hours or so. Worse, knowing which cylinder(s) have bad valve guides is also difficult to determine. My IA and I have a few hunches based on borescopy views. The valves with bad guides might be the valves observed leaking oil into the cylinders. Pulling the valve covers to look for valve guide blow-by might also be helpful.

I am skeptical of turbo oil leakage being the source of any significant oil loss. After majoring my engine, I had problems with turbo oil leakage for the first few years after the overhaul. I figured out that that leakage was due to a leak between the oil scavenging line fitting and the starter adapter. If that interface leaks, it will leak air into the system, and not oil out. That will interfere with the effectiveness of the oil scavenging from the turbo, resulting in the turbo leaking excess oil out. I fixed the issue with a del seal between the scavenging hose fitting and the starter adapter. Del seals are available here.

Hope this helps.

Paul Keller

 

[A64Pilot]

A quart in ten hours is nothing, I would in fact be concerned if it didn’t burn at least that. Most airplanes burn more than that, a great many quite a bit more.

[Fix]

I get different oil level readings depending what way my oil dip stick points.

It differs 1qt

Not sure why, but that confused me a bit before I always have oil dip stick at same direction now.

What is the correct position?

[Pinecone]

Engine is a factory reman, about 300 hours.

I finally got over the airport to check the oil, and in 9.2 hours, it burned about 1/2 a quart.  That was 2.2 flying an IPC at the Mooney PPP, and 7.0 hour home at 17,000, non-stop.

I did talk to Main Turbo and they recommended checking the oil scavenging with a simple test.  Also suggested checking the waste gate.

As for the position of the dipstick, the only way that really works in mine is with the finger loop towards the tail

[Fix]

54 minutes ago, Pinecone said:

As for the position of the dipstick, the only way that really works in mine is with the finger loop towards the tail

Agree, have it loop pointed towards tail too.

[anthonydesmet]

15 hours ago, Pinecone said:

As for the position of the dipstick, the only way that really works in mine is with the finger loop towards the tail

I was going to ask you this question also.  Loop to the tail here too.

[Z W]

Well now we have another Mooneyspace controversy.  Mine has always been loop towards the nose.  I didn't know you could reverse it.  I'll have to try and see what that does. 

[M20F]

15 hours ago, Pinecone said:

Engine is a factory reman, about 300 hours.

I finally got over the airport to check the oil, and in 9.2 hours, it burned about 1/2 a quart.  That was 2.2 flying an IPC at the Mooney PPP, and 7.0 hour home at 17,000, non-stop.

I did talk to Main Turbo and they recommended checking the oil scavenging with a simple test.  Also suggested checking the waste gate.

As for the position of the dipstick, the only way that really works in mine is with the finger loop towards the tail

So you had one indication on one flight where it burned 1 quart more than normal, all other flights (it appears to be 4 plus a 7hr high altitude flight) burned per normal?

[Pinecone]

It used 2 quarts in 6.9 hours.  After filling, it used 1/2 a quart in 11 hours (4 hours low altitude, 7 hours high altitude). 

[Will.iam]

On 10/25/2024 at 3:46 PM, Pinecone said:

Engine is a factory reman, about 300 hours.

I finally got over the airport to check the oil, and in 9.2 hours, it burned about 1/2 a quart.  That was 2.2 flying an IPC at the Mooney PPP, and 7.0 hour home at 17,000, non-stop.

I did talk to Main Turbo and they recommended checking the oil scavenging with a simple test.  Also suggested checking the waste gate.

As for the position of the dipstick, the only way that really works in mine is with the finger loop towards the tail

Would you mine telling us the simply test they described for checking the oil scavenging?

[Pinecone]

Take both the oil supply and oil return off the turbo, remove check valves.  Put both hoses into a container with some oil.   Turn the engine over with the starter for 45 - 60 seconds.

Oil level in the container should go down, meaning oil scavenge pump is pulling more oil than the oil supply it pumping out.

[231MJ]

That's a great way to check the scavenger pump. Thanks for the idea.

Last weekend I had fresh/clean oil dripping onto the hangar floor on the turbo side of the engine (oil was changed a few hours ago so it was still clean) and the nose gear was kinda soaked.  Took off the cowling and found oil on the turbo side of the engine and oddly, the bottom of the turbo had oil on it but not on top.  The waste gate had no oil on it.  No oil dripping from the exhaust.  No oil inside the induction side of the turbo.  The pushrod tubes were resealed two years ago so I don't suspect they are the issue, plus a leak from there would not bet to the bottom of the turbo but not the top.  I washed the engine (several times) and will test run next weekend to see if I can find the leak.

Are there any shops that are overhauling the check valves?  

 

 

[Pinecone]

If your first try doesn't find the leak, skip messing around and get some of the UV dye to put into the oil. 

Clean the engine, add the dye, run about 2 - 3 minutes, POW, oil leak is clear.

Yes, a leaking pushrod tube will put oil on the top of the turbo.  BT, DT.