New fluctuation in oil pressure

[AeroEng]

I would very much appreciate the brain trust’s input on this one. 
 

I just had the plane into the shop. I’m trying to track down a recent (last 30 hours) increase in oil burn rate. During that visit, the mechanic also installed a new TIT sensor (probably not relevant, but mentioning it in case the group thinks this is a sensor issue and maybe something was jostled). 

Anyway, after picking up the plane from the mechanic, I made a long flight from KSUS down to KPIE (about 4 hours). About a third of the way there, I climbed from around 12k up to 15.5k to get over some cloud cover.  Immediately after the climb, my oil pressure r began to fluctuate from its normal pressure of 57. It would drop five, then go back up, then drop 8 and go back up. Then down 3 and back up. Etc. A graph output of the oil pressure is attached. The pressure never went below green and never below 45ish.  But the drops are not slow and steady, they are sharp. 
 

I’ve looked at all the prior flights and never had this issue.  It seems new.  Is it possibly just a sensor issue given the recent TIT probe install?  Anyone have any other good thoughts?  Really appreciate the help from all the sages the forum.

 

 

 

 

 

[201Mooniac]

Which engine is this and how much is the increase in oil consumption?

[Ethan]

It would also be helpful to know what kind of oil pressure monitor you have. 

[AeroEng]

Sorry, should have provided those details.  This is on a 2007 Acclaim with a Continental TSIO 550-G.  Monitoring is done through the G1000.  

[AeroEng]

Oil consumption seems to be about 1 quart every two hours.  Up from 1 quart every four hours.  

 

I know the continental engines can slowly refill over a few days after running.  I started at 7.5 quarts, then flew for four hours.  The day after the flight, I checked and the oil was down to 5.5 quarts.  I plan to check again tomorrow to see if it crept back up at all.  But the burn rate is definitely higher. 

I also had some good soot on the belly of the plane behind the exhaust and all the way down the underside.  But only on the left side (where the oil breather tube is located).  

[N201MKTurbo]

I have found that oil pressure anomalies are never good. It usually means that oil is leaking somewhere where it doesn’t usually leak. When I say leak, I mean like leaking past a bearing or gear shaft, not leaking out of the engine. 
 

I would check your suction screen and filter for metal.

I can’t imagine a problem that would cause a drop in oil pressure and an increase in consumption.

[201Mooniac]

1 minute ago, N201MKTurbo said:

I have found that oil pressure anomalies are never good. It usually means that oil is leaking somewhere where it doesn’t usually leak. When I say leak, I mean like leaking past a bearing or gear shaft, not leaking out of the engine. 
 

I would check your suction screen and filter for metal.

I can’t imagine a problem that would cause a drop in oil pressure and an increase in consumption.

Maybe a broken ring?  When I had a broken ring in my Lyc IO-360 I had decreasing pressure and high consumption.

[Fly Boomer]

50 minutes ago, AeroEng said:

I also had some good soot on the belly of the plane behind the exhaust and all the way down the underside.  But only on the left side (where the oil breather tube is located).  

Broken ring(s) and excessive blow-by?  I'm no mechanic.

EDIT:  @201Mooniac beat me by a nose.

[N201MKTurbo]

1 hour ago, 201Mooniac said:

Maybe a broken ring?  When I had a broken ring in my Lyc IO-360 I had decreasing pressure and high consumption.

A broken ring can cause increased consumption, but the rings are not in the oil system flow path, so how would they affect oil pressure? It could pressurize the crankcase, which could have a small effect on oil pressure.

[N201MKTurbo]

FWIW, I did have a broken ring once that did cause the oil pressure to fluctuate, because all the oil went away. I don't think the OP stated that he had less than 2 Qts in the engine when he landed.

[PT20J]

Any failure immediately after maintenance is cause for suspicion that the two are related -- even more so in this case since the maintenance involved the engine monitor. I would check all the wiring to the oil pressure transducer to see if something has changed or is loose. If I couldn't find anything, I would try to reproduce it on the ground and if I could do that then I would plumb in an analog pressure gauge to determine if it is a real fluctuation or an instrumentation problem.

Skip

[201Mooniac]

22 minutes ago, N201MKTurbo said:

A broken ring can cause increased consumption, but the rings are not in the oil system flow path, so how would they affect oil pressure? It could pressurize the crankcase, which could have a small effect on oil pressure.

Not sure of the mechanism, just what I noticed.  It was the fluctuation that caused me to land early of my destination and find the noticably increased oil consumption.

[PT20J]

A quart every 2-4 hours sounds like a lot for a Continental. It may be that the oil consumption and the oil pressure fluctuation are unrelated. I would investigate the oil consumption. It sounds from your descriptions that it is getting burned and not leaking. It can only get burned if it's getting past the valve stems or the piston rings. I'd do a borescope exam and compression test and check the filter were it mine in addition to determining that the instrumentation is correct.

[AeroEng]

57 minutes ago, N201MKTurbo said:

FWIW, I did have a broken ring once that did cause the oil pressure to fluctuate, because all the oil went away. I don't think the OP stated that he had less than 2 Qts in the engine when he landed.

I still had at least 5.5 quarts when I landed. It wasn’t in oil starvation mode. 

[AeroEng]

26 minutes ago, PT20J said:

A quart every 2-4 hours sounds like a lot for a Continental. It may be that the oil consumption and the oil pressure fluctuation are unrelated. I would investigate the oil consumption. It sounds from your descriptions that it is getting burned and not leaking. It can only get burned if it's getting past the valve stems or the piston rings. I'd do a borescope exam and compression test and check the filter were it mine in addition to determining that the instrumentation is correct.

Got it. I’m going to do this as soon as I’m home from this trip. I’ll also check all the wiring as Skip recommended. 

Thanks as always for the great advice. 

[Guest]

Broken or stuck piston rings in one or more cylinders, 550’s are known for this in my experience.  How dark is the oil? Blowby from stuck rings will darken your oil quickly.  Cylinder and spark plug examination and should point you to the offending cylinder.

No suction screen to check on your 550, it’s internal to the engine.  Only your filter for examination.

[AeroEng]

2 hours ago, M20Doc said:

Broken or stuck piston rings in one or more cylinders, 550’s are known for this in my experience.  How dark is the oil? Blowby from stuck rings will darken your oil quickly.  Cylinder and spark plug examination and should point you to the offending cylinder.

No suction screen to check on your 550, it’s internal to the engine.  Only your filter for examination.

If bad rings are the culprit, how quickly do I need to take action to get it fixed?  Is this a “don’t fly the plane home” situation or a “fly the plane home, but get it looked at ASAP once you get there” situation?

 

thanks…

[GeeBee]

Worn rings you can fly if you have enough oil to get there. A broken ring is grounding. 

[AeroEng]

2 hours ago, GeeBee said:

Worn rings you can fly if you have enough oil to get there. A broken ring is grounding. 

Got it. Thanks.  I’m assuming broken ring would show up in the oil filter.  I’ve had clean filters…

Thanks again for all the help from this group. It is really special that us newbies can come here and get great advice. 

[takair]

I’m far from a turbo expert, but I’ll throw this out there.  You climbed and the fluctuation started.  Is this possibly turbo related..one side.  Leaking oil seal in the turbo might manifest itself with a change in pressure…altitude.  I think this can appear in the exhaust….and would certainly impact oil burn rate.  Turbo experts?  Analysis of spark plugs can tell you if you have a broken ring.  Would theoretically change the appearance of only one set of plugs.  Relatively easy check on the road.

[LANCECASPER]

22 hours ago, AeroEng said:

I would very much appreciate the brain trust’s input on this one. 
 

I just had the plane into the shop. I’m trying to track down a recent (last 30 hours) increase in oil burn rate. During that visit, the mechanic also installed a new TIT sensor (probably not relevant, but mentioning it in case the group thinks this is a sensor issue and maybe something was jostled). 

Anyway, after picking up the plane from the mechanic, I made a long flight from KSUS down to KPIE (about 4 hours). About a third of the way there, I climbed from around 12k up to 15.5k to get over some cloud cover.  Immediately after the climb, my oil pressure r began to fluctuate from its normal pressure of 57. It would drop five, then go back up, then drop 8 and go back up. Then down 3 and back up. Etc. A graph output of the oil pressure is attached. The pressure never went below green and never below 45ish.  But the drops are not slow and steady, they are sharp. 
 

I’ve looked at all the prior flights and never had this issue.  It seems new.  Is it possibly just a sensor issue given the recent TIT probe install?  Anyone have any other good thoughts?  Really appreciate the help from all the sages the forum.

In your logbooks have the service bulletins been done on your Acclaim that deal with the hoses that enter and exit the air/oil separator?

(This is a known issue on the TSIO-550-G on the Acclaim. If the people who did your pre-buy knew Acclaims I'm sure they looked at this to see if it was done.)

The black hose that runs from the air/ol separator down to your left exhaust pipe could be clogged. Or the yellow Tygon hose that runs from the oil filler tube back to the separator gets clogged and I believe that either of those would raise the crankcase pressure.

https://www.mooney.com/wp-content/uploads/2020/12/SBM20-312.pdf

https://www.mooney.com/wp-content/uploads/2020/12/SBM20-319.pdf

 

(It would be good to post this in the Acclaim owners section since other new owners may run into this as well. Also a good idea to update your profile to show which airplane y0u fly so people can be more helpful.)

 

[Guest]

5 hours ago, AeroEng said:

If bad rings are the culprit, how quickly do I need to take action to get it fixed?  Is this a “don’t fly the plane home” situation or a “fly the plane home, but get it looked at ASAP once you get there” situation?

 

thanks…

It depends on the oil consumption rate.  Running your engine low on or out of oil is quite costly.  Dark oily spark plugs and oily pistons are the indicators for which cylinders are ill.  

[PaulM]

On 8/2/2022 at 11:31 AM, AeroEng said:

 Immediately after the climb, my oil pressure r began to fluctuate from its normal pressure of 57. It would drop five, then go back up, then drop 8 and go back up. Then down 3 and back up. Etc. A graph output of the oil pressure is attached. The pressure never went below green and never below 45ish.  But the drops are not slow and steady, they are sharp. 
 

I

Spiky fluctuations are often wiring related.   I have found that both the MP and Oil Pressure sensor connectors in the G1000 will get dirty and exhibit this sort of issue.   If I suspect this you take the top cowl off,  remove both connectors, clean with contact cleaner and put them on and off a couple of times to wipe the contacts. 

[PT20J]

3 hours ago, AeroEng said:

Got it. Thanks.  I’m assuming broken ring would show up in the oil filter.  I’ve had clean filters…

Thanks again for all the help from this group. It is really special that us newbies can come here and get great advice. 

Eventually. When my IO-360 Lycoming broke an oil control ring, pieces of ring were captured by the suction screen (removable in that engine) and there was aluminum metal in the filter because the ring took out a hunk of the piston. The engine was burning about 2hrs/qt when I bought it but otherwise ran fine. During a pre-purchase inspection by Don Maxwell it had a clean oil filter, recent OK oil analysis, high 70's compressions and the borescope inspection only showed some minor pitting and no excessive oil. I don't know if the ring was stuck or broken at the time of the pre-purchase inspection, but 25 hours later during annual inspection the engine was trash. We even found metal particles embedded in the con rod big end. Interesting thing is that the engine appeared to be running fine at the time and making good power. But, it was probably only a few hours away from a nasty failure.

Skip

[GeeBee]

4 hours ago, AeroEng said:

Got it. Thanks.  I’m assuming broken ring would show up in the oil filter.  I’ve had clean filters…

Thanks again for all the help from this group. It is really special that us newbies can come here and get great advice. 

You can get good advice here and I am the one who gave you what you quoted. I would caution you one thing. Advice is worth what you pay for it. I see you have Savvy analysis. I would, if I were you, at least invest in Savvy Q&A if not higher particularly with the high performance airplane you are flying. I have Q&A and have used it several times, if only for a sanity check. I recently came off a bad CHT probe situation and I used Q&A as a sanity check just to make sure I did not have a detonation situation.