Oil pressure decreasing?

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SepticTank

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SepticTank
For context, I fly with an O-540 and the oil & filter were changed about 5 hours ago with 15w-50.

Went on a flight today that started off normal, but about 10 minutes in I thought my engine started sounding rough (could've been imaginary) and I noticed my oil pressure started dropping by 1 PSI about every 2-5 seconds so I turned back towards the field; the oil temps remained stable and in the green. I typically see about 75 PSI in cruise, but was down to 59 PSI by the time I entered the pattern and 55 PSI (Lycoming's minimum) when I was turning final.

I taxied back and did another runup, which was normal and proceeded to takeoff again. By the time I was 100' in the air my oil PSI was at 80 (typically at 95). I had the same issue around the pattern and took the plane in for the day.

Any thoughts or ideas as to what this could be? All other gauges were operating normally and it was about 80 degrees. I've have flown without issue in much higher and lower temps.
 
Rgbeard said:
Wow - you had an undetermined major issue and took off a second time?

Ummmm. Wow. That's some interesting ADM there!!!

Do you have a family? Simply curious.
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Thanks for your contribution. You don’t have to be a dick.
 
SepticTank said:
Thanks for your contribution. You don’t have to be a dick.
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Well, I think it was an appropriate response. You're quite welcome.

Any variation in oil pressure off the norm is a bad, bad thing, and this won't fix itself. You risked your life here, and it worked out okay - THIS TIME.
 
SepticTank said:
Thanks for your contribution. You don’t have to be a dick.
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Pointing out a bad decision you made doesn’t make someone a dick and frankly, I’m wondering why’d you’d elect to takeoff a second time with an anomaly like that too. That’s not just a “let’s check and see” type of thing. That was not a smart decision.
 
Ignoring taking off with a known problem aside, at what power settings were you seeing the oil pressure loss.??

What gauge will measure oil pressure in 1 pound increments.??
 
Zeldman said:
Ignoring taking off with a known problem aside, at what power settings were you seeing the oil pressure loss.??

What gauge will measure oil pressure in 1 pound increments.??
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I noticed the loss between 1500 and 2200. I have a digital engine monitor that gives readings in 1 PSI increments and while I understand there’s some variance there was definitely a trend.
 
Was the oil level normal before you took off? And was this the same oil you were using before?
 
Since you choose not to put your general location in your profile we don’t know your climate.

Given that it’s now June, most anywhere in the country has gotten warmer in the last weeks. Warmer ambient will result in a certain amount of lowered oil pressure. In my fresh 30 hour engine I have seen noticeably lower oil pressure with the onset of Texas Summer. Consult 6our POH and ensure that your idle and cruise oil pressure falls within limits and be happy. If it’s falling outside acceptable limits, then dig into it.
 
It was normal when I took off and about 3 quarts low when I checked it right after I landed, though much of that oil could’ve still been in the engine.

If going by the low number, it was still above the minimum operating amount
 
Possibly sensor failure? With decreased pressure, I would expect to see decreased flow and therefore higher temps. Absent the temps, this reads like a sensor.

need to check the oil after it’s drained out.
 
Okay, if you’re losing that much oil that’s a whole different kettle of fish. You lost 3 quarts in how many hours of flight?
 
My thought would be to consult your mechanic before you try to see if it happens again.
 
MBDiagMan said:
Okay, if you’re losing that much oil that’s a whole different kettle of fish. You lost 3 quarts in how many hours of flight?
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15 minutes of flight. But I checked it before the oil had time to settle in the pan so there might not be oil loss. I’ll know more this weekend when I can get back up there to check it
 
I would suspect oil filter , suction screen and oil drain in that order . A loose filter would account for quantity and pressure loss. And you would have a mess in cowling.
 
Rgbeard said:
Wow. For a 12qt sump system, running 6 is definitely an interesting choice.

Has your mech checked screen?
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Do you have much experience with the O-540?Anything over 8 gets burped out..
 
Was your dipstick properly secured? I lost a quart of oil pretty quickly one day when I left the dipstick unsecured. The crankcase vent was cut to create a partial vacuum, so I got a lot of airflow (and oil flow) through the engine. The oil ended up on the belly.

Which brings up the real question - where'd the oil go? No way you leaked or burned that much oil quickly without it leaving evidence of where it went.
 
SepticTank said:
No. The temp remained normal
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Define "normal". Are we talking about "in the green" or are we talking about having the same oil temperature as you always do? There's a big difference.

SepticTank said:
It was normal when I took off and about 3 quarts low when I checked it right after I landed, though much of that oil could’ve still been in the engine.

If going by the low number, it was still above the minimum operating amount
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If you lost three quarts of oil in such a short flight you need to figure out where it went. Something is wrong with this engine.

SepticTank said:
Do you have much experience with the O-540?Anything over 8 gets burped out..
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In my experience with numerous 540s, that would be abnormal.

What kind of aircraft is this?
 
Add a quart when it hits 8. Doesn't go out the breather until it's more than 9.5. Long flight I'll add at 8.5... I don't even start my O-360 with 6 quarts or less.
 
I believe it’s safe to say there’s a significant mechanical issue. I am guessing something is cracked somewhere.

I can’t put my hands on my keyboard/screen and do anything better at diagnosis but I can certainly say this plane should be considered grounded until the problem is rectified.
 
SepticTank said:
For context, I fly with an O-540 and the oil & filter were changed about 5 hours ago with 15w-50.

Went on a flight today that started off normal, but about 10 minutes in I thought my engine started sounding rough (could've been imaginary) and I noticed my oil pressure started dropping by 1 PSI about every 2-5 seconds so I turned back towards the field; the oil temps remained stable and in the green. I typically see about 75 PSI in cruise, but was down to 59 PSI by the time I entered the pattern and 55 PSI (Lycoming's minimum) when I was turning final.

I taxied back and did another runup, which was normal and proceeded to takeoff again. By the time I was 100' in the air my oil PSI was at 80 (typically at 95). I had the same issue around the pattern and took the plane in for the day.

Any thoughts or ideas as to what this could be? All other gauges were operating normally and it was about 80 degrees. I've have flown without issue in much higher and lower temps.
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You said engine ran rough. That makes it real, not a loose probe or bad gauge.
 
SepticTank said:
3 is the minimum. I usually keep it no lower than 6. It was at 6 today when I took off.
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You fly an O-540 with only 6 quarts?!

I will do a lap or two around the pattern at 8.5 quarts but really anywhere under 9 and it gets more oil added.
 
Someone asked a question about your oil type and if you have changed the type, or weight of oil recently. I recommend confirming in the log book if your not absolutely sure. Changing oil weights can definitely make a small difference, but it would be a consistent difference, not varying as you’ve described.

I used to fly once or so a month (last flight was yesterday) a twin with IO540’s for a corporate outfit. They didn’t want us to leave home for an out & back without 9.5 qts., but we flew long flights. 7 hour out & backs were not uncommon.

You’re oil quantity numbers don’t seem to add up.
What’s the lowest and highest oil quantity that you operate?
What’s the lowest you have been taking off with? What’s the lowest you’ve found the oil quantity after flying (when checked properly, once it’s settled) and how much of a drop was that per flight hour?
What color (how dark) is the inside of your exhaust pipes?
 
kyleb said:
Was your dipstick properly secured? I lost a quart of oil pretty quickly one day when I left the dipstick unsecured. The crankcase vent was cut to create a partial vacuum, so I got a lot of airflow (and oil flow) through the engine. The oil ended up on the belly.

Which brings up the real question - where'd the oil go? No way you leaked or burned that much oil quickly without it leaving evidence of where it went.
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agree, that oil has to be some where on the aircraft. Might check the oil filter area pretty thoroughly. If the old filter gasket didn’t come off w/the filter - and then the are two - not, not good.
 
Mxfarm said:
agree, that oil has to be some where on the aircraft. Might check the oil filter area pretty thoroughly.
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Maybe, but not necessary. I think he would know if 3 quarts leaked out:) I’d like for him to check the exhaust color, take pics. He could have cylinder issues causing an excess amount to blow pass by the rings.
 
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Jdm said:
Maybe, but not necessary. I think he would know if 3 quarts leaked out:) I’d like for him to check the exhaust color, take pics. He could have cylinder issues causing an excess amount to blow pass by the rings.
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to burn 3 qts through the cylinders in that time frame would be - impressive :eek:
 
I’ve never been a fan of 15-50. If any oil would contribute to low pressure it’d be 15-50. The 3 quarts missing would get my full attention. I wouldn’t fret about reading one quart off right after shutting down but 3 quarts isn’t normal.
 
Jdm said:
I’d like for him to check the exhaust color, take pics. He could have cylinder issues causing an excess amount to blow pass by the rings.
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FYI: 3 quarts through the rings would be very evident on the plugs.
 
Bell206 said:
FYI: 3 quarts through the rings would be very evident on the plugs.
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Yes, but based on the description I’m not sure if he’s able to remove plugs, or does any owner maintenance. He also reported a roughness, which could be an indication of plug saturation.
 
Burning three quarts of oil on a 15 minute flight would be evident by the cloud of smoke coming from the exhaust. Seriously ...
 
Some years ago a guy reported his 0~290 D TriPacer would “ puke oil” only under some circumstances. One day I flew it and I could HEAR the oil hitting the belly.
Fast Forward - The Cam had been replaced at Major and it was TOO LONG.
This allowed oil to be pumped out the front breather; RAPIDLY.

Two weeks ago I got a call re a similar engine. Since this was a EXP he was able to fabricate a breather from the unused Vac Pump Pad.
 
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