Oil consumption

[M20F]

Airplane runs fine other than consuming 1qt of oil an hour.  Oil is discharging through exhaust.  All plugs clean except for #2 which are oily (top and bottom).  All cylinders make appropriate compression including #2. 
 
Did the MMO routine on #2, ran a bit with MMO in case, flushed.  Same issue 1hr later oiled plugs and 1qt gone.  Borescope shows clean walls (no scoring).  Plane was in for 6 month annual for parts so didn’t fly.  Oil consumption started halfway through a 12hr trip.  So if it was stuck think between MMO and flying would have shook loose.  CHT/EGT all normal (MVP-50). 
 
My thought is a broken oil ring.   Your thoughts or others things to look at?  I am going to get the cylinder pulled next week but before I did figure I would poll the peanut gallery.  

[vik]

All symptoms point to either a broken or stuck oil ring. If found broken, be sure to measure the grooves in the piston to be sure it is still within the tolerance. A broken ring can also ruin the piston.

If new piston is needed, call Combustion Tech with the weight of your old piston. They weight the pistons after production and will try to find one close to yours.

Vik

 

[RLCarter]

Be interesting to see what is found… you mentioned that it sat for 6 month’s waiting on parts, was there any work done on the engine during that time?

[Dialed In]

I would also check your turbo. I have had seals fail on both the turbine and compressor side, more often the compressor side. All you have to do is check your induction tubing for oil residue, if it’s bad it will be dry from the filter to the turbo then from the turbo to the servo will be wet. You can also check the exhaust manifold before the turbo is there residue there or just after the turbo? They can pump a lot of oil out in short order if they completely fail. I would agree that it sounds like an oil ring on #2 but the turbo is probably worth a quick check. 

[M20F]

14 hours ago, Dialed In said:

I would also check your turbo. I have had seals fail on both the turbine and compressor side, more often the compressor side. All you have to do is check your induction tubing for oil residue, if it’s bad it will be dry from the filter to the turbo then from the turbo to the servo will be wet. You can also check the exhaust manifold before the turbo is there residue there or just after the turbo? They can pump a lot of oil out in short order if they completely fail. I would agree that it sounds like an oil ring on #2 but the turbo is probably worth a quick check. 

Induction tubing has no oil.  The scavenger pump was the originally thought culprit and that has a fresh overhaul now. 

[M20F]

16 hours ago, RLCarter said:

Be interesting to see what is found… you mentioned that it sat for 6 month’s waiting on parts, was there any work done on the engine during that time?

No was an easy annual at Maxwells just had to wait for some hoses and the elevator weights so took forever. 

[Greg Ellis]

I am having almost the exact same problem except mine is on the #1 cylinder so I am interested in following this.  Mine is also moving through oil like crazy.  It sits in my hangar until my mechanic can get to it. The cylinder was recently (about 40 hours or so) IRAN'd for a new exhaust valve which was replaced and looks good on the borescope.  Nothing else was mentioned wrong with the cylinder and everything else looked good according to the overhaul shop and my mechanic.  Both plugs very wet with oil.  A couple of borescope photos of the cylinder with oil for your viewing pleasure....  I am no mechanic but looking at the photos of the walls of the cylinder I am not sure if they look good or not.  It is a nitride hardened steel cylinder.

[DXB]

15 minutes ago, Greg Ellis said:

I am having almost the exact same problem except mine is on the #1 cylinder so I am interested in following this.  Mine is also moving through oil like crazy.  It sits in my hangar until my mechanic can get to it. The cylinder was recently (about 40 hours or so) IRAN'd for a new exhaust valve which was replaced and looks good on the borescope.  Nothing else was mentioned wrong with the cylinder and everything else looked good according to the overhaul shop and my mechanic.  Both plugs very wet with oil.  A couple of borescope photos of the cylinder with oil for your viewing pleasure....  I am no mechanic but looking at the photos of the walls of the cylinder I am not sure if they look good or not.  It is a nitride hardened steel cylinder.

 

In my (admittedly  limited) experience, finding oil on the top plug of one cylinder and a pool of oil inside it is pretty much a smoking gun for which one is the offender and needs to get pulled off.  That's very frustrating that this one was IRAN'd a mere 40 hours ago.  I think it's standard to rehone the cross hatch and change the rings whenever a cylinder comes off? I don't see much cross hatch here, and maybe there's some deep scuffs.

[Shadrach]

29 minutes ago, DXB said:

 

In my (admittedly  limited) experience, finding oil on the top plug of one cylinder and a pool of oil inside it is pretty much a smoking gun for which one is the offender and needs to get pulled off.  That's very frustrating that this one was IRAN'd a mere 40 hours ago.  I think it's standard to rehone the cross hatch and change the rings whenever a cylinder comes off? I don't see much cross hatch here, and maybe there's some deep scuffs.

There is no reason to re-ring and re-hone a removed cylinder if those parts are in good working order. 

[LOCOLJ]

2 hours ago, M20F said:

Induction tubing has no oil.  The scavenger pump was the originally thought culprit and that has a fresh overhaul now. 

I had an issue where I lost oil out of the exhaust due to a loose fitting on the scavenge pump.  Since they rebuilt it, make sure it is tight.

[M20F]

5 hours ago, LOCOLJ said:

I had an issue where I lost oil out of the exhaust due to a loose fitting on the scavenge pump.  Since they rebuilt it, make sure it is tight.

If the scavenger pump was the problem it would be pushing oil through the turbo seals.  The only way the #2 cylinder plugs would get oil is if it was going out the discharge side of the turbo into the intake.  I see zero indication  of oil coming through that pipe and all the other plugs are clean.  Thus don’t think it is the pump. 

[M20F]

5 hours ago, Shadrach said:

There is no reason to re-ring and re-hone a removed cylinder if those parts are in good working order. 

In my case I will probably do a new piston and rings because why not when it is off.  Based on what the barrel looks like we will determine a rehone.   It looks good on the borescope so hopefully we can avoid the machining not so much for the cost but because the airplane will be down another 6yrs given things these days.  

[Shadrach]

2 hours ago, M20F said:

In my case I will probably do a new piston and rings because why not when it is off.  Based on what the barrel looks like we will determine a rehone.   It looks good on the borescope so hopefully we can avoid the machining not so much for the cost but because the airplane will be down another 6yrs given things these days.  

My compressions at last annual 80/80, 80/80, 80/80, 79/80. Borescope looked healthy. It burns a qt every 10-15hrs depending on operations and OAT. If I had something like a crankcase crack the necessitated splitting the case, I doubt I would replace anything on the cylinders unless something unknown was revealed during disassembly.
I have every indication that the interface between my cylinders, rings and pistons  is ideal.

What is the upside to starting over from ideal?

[M20F]

Finally got my ancient garbage borescope working.  Puddle of oil, taking it out to Cole to get pulled.  I hate airplanes. 

[ArtVandelay]

In my case I will probably do a new piston and rings because why not when it is off.

Might want to find out the current wait time is (and I would double whatever estimate they give you) to get new before making a decision.

[M20F]

9 minutes ago, ArtVandelay said:

Might want to find out the current wait time is (and I would double whatever estimate they give you) to get new before making a decision.

You can’t get them repositioned where they were so they will have to wear to reseat again.  In a pinch rebuilding a beater car engine for expediency I have reused rings, but I would never reuse for anything I valued.  All reusing them does is assure you in the near future you will have a problem. 
 
Certainly we can make arguments around infant mortality and a bunch of other things.  Personally though reusing rings is a no go for me. 

[N201MKTurbo]

2 hours ago, M20F said:

You can’t get them repositioned where they were so they will have to wear to reseat again.  In a pinch rebuilding a beater car engine for expediency I have reused rings, but I would never reuse for anything I valued.  All reusing them does is assure you in the near future you will have a problem. 
 
Certainly we can make arguments around infant mortality and a bunch of other things.  Personally though reusing rings is a no go for me. 

I have pulled cylinders and put them back on without replacing the rings, they worked just like before. 
 

My thoughts are that rings and pistons should be replaced as a set. Putting new rings on a used piston is as bad as putting used rings on a new piston.

The rings seat on the cylinder walls, but they also seat on the piston grooves. To a certain degree, the sealing on the piston grooves will improve over time as the grooves fill with deposits and the deposits end up forming the seal.