Oil pressure decreasing?

Doesn’t sound like the cowling has been off since the event.
 
Daleandee said:
Burning three quarts of oil on a 15 minute flight would be evident by the cloud of smoke coming from the exhaust. Seriously ...
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That engine would die in flight if it was burning that much. The plugs would be shorted right out.
 
Mxfarm said:
to burn 3 qts through the cylinders in that time frame would be - impressive :eek:
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I had a 172XP go from 10 qts to 3 qts in a 20-minute flight to maintenance. The local FSS actually got a call from the sheriff because somebody reported an airplane going down.:eek:

Had a cracked piston.

...and just to make the OP feel a little better, he’s not the only one who’s ever taken an airplane into the air with something not right. ;)
 
MauleSkinner said:
I had a 172XP go from 10 qts to 3 qts in a 20-minute flight to maintenance. The local FSS actually got a call from the sheriff because somebody reported an airplane going down.:eek:

Had a cracked piston.

...and just to make the OP feel a little better, he’s not the only one who’s ever taken an airplane into the air with something not right. ;)
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But if, after this thread, he keeps it up, the NTSB will be doing the troubleshooting, not POAers.
 
According to Lycoming, a O-540 will run fine without damage till 2 3/4 quarts. Flying around with 6 quarts isn’t going hurt a thing. In my o-540, anything over 8 quarts gets thrown over. Aircraft engines are certified for twice the oil they actually need, pretty common knowledge
 
Daleandee said:
Burning three quarts of oil on a 15 minute flight would be evident by the cloud of smoke coming from the exhaust. Seriously ...
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Dan Thomas said:
That engine would die in flight if it was burning that much. The plugs would be shorted right out.
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Mxfarm said:
to burn 3 qts through the cylinders in that time frame would be - impressive :eek:
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Yep, agree with all of this. Never considered the possibility that he actually burned 3 qts in 15 minutes!
I said he could have cylinder issues causing an “excess” amount to blow pass by the rings.
I think it’s likely there’s a combination of things going on here. He’s could be blowing a lot through the cylinders. He might not be exactly clear how much was in there in the first place, or how much was actually there afterwards, there could be leaks as well.
 
Dan Thomas said:
That engine would die in flight if it was burning that much. The plugs would be shorted right out.
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That was kinda the point I was after. I don't see how it would continue to run if it did start. Three quarts in fifteen minutes is an enormous amount to pump through a cylinder (or four). Seems that hydraulic lock would be a concern. Something smells fishy here ...
 
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.
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With all this talk about how much oil was missing, burnt, or puked, I’m waiting to hear how much oil is actually in the engine when he takes a reading again.
 
TrueCourse said:
With all this talk about how much oil was missing, burnt, or puked, I’m waiting to hear how much oil is actually in the engine when he takes a reading again.
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Right. If it leaked this much it’d be dripping off the damn rudder. I’ve actually seen that! It can’t possibly burn this much, even with ratty cylinders. Must be a combination of things, including uncertain oil levels, and consumption.
 
TrueCourse said:
With all this talk about how much oil was missing, burnt, or puked, I’m waiting to hear how much oil is actually in the engine when he takes a reading again.
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Checking the oil after landing is what he said. The oil being hot would flow pretty quickly to the sump and it would take a few minutes to get out of the plane and check the oil. I don't see the engine hiding three quarts of oil unless a return is blocked and the rocker covers are full. Again ... smells like a seafood market to me. :dunno:
 
Lot of oil burning also causes detonation, which breaks pistons and blows cylinders off.
 
I had a mech do a twelve-qt fillup and I had oil dripping from the tie-down ring!

that said. I am guessing 1qt was “in the engine”, and two qts disappeared.

In any case I am guessing something, somewhere is cracked.
 
Alright folks, I checked the oil level now that the engine has cooled and it didn’t burn any oil.. still at 6 quarts
 
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So, reduced oil pressure, no increase in oil temp.

Low-hanging fruit is a sticking pressure regulator; can get a chunk of carbon/gradoo/grunge on the seat and lets more oil through than proper, yielding a reduced pressure reading. Could also have a broken spring, which could mimic the symptoms described.

Right-off, though, I'd remove, cut open and inspect (closely) the oil filter, looking for *any* evidence of metal from engine internals. Assuming that's clean, I'd then look at the oil pressure regulator because [what I wrote above]. If you find metal, of course, you're diving inside to see what it is - what you find will guide you further.

But the take-away you need: it ain't "nothing" (oil pressure does not change that much all by itself). I'd ground until a clear culprit is identified, and a demonstrated fix, completed.
 
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SCCutler said:
So, reduced oil pressure, no increase in oil temp.

Low-hanging fruit is a sticking pressure regulator (some call it the "vernatherm"); can get a chunk of carbon/gradoo/grunge on the seat and lets more oil through than proper, yielding a reduced pressure reading. Could also have a broken spring, which could mimic the symptoms described.
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The Vernatherm controls the oil temperature, not its pressure. The pressure relief valve governs the pressure.

Edit:

upload_2022-6-25_20-37-7.png
 
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(Head hangs in shame).

What I get for posting drunk.

Ignore all remaining references to the vernatherm. Like he said.

(Shuffles off to slit wrists).
 
Garee said:
According to Lycoming, a O-540 will run fine without damage till 2 3/4 quarts. Flying around with 6 quarts isn’t going hurt a thing. In my o-540, anything over 8 quarts gets thrown over. Aircraft engines are certified for twice the oil they actually need, pretty common knowledge
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Beware of generalized advice. The OP has a Continental IO-520. That engine has very specific oil quantity requirements depending on the airframe it’s installed in. That airplane’s AFM will state oil requirements.
 
Stewartb said:
Beware of generalized advice. The OP has a Continental IO-520. That engine has very specific oil quantity requirements depending on the airframe it’s installed in. That airplane’s AFM will state oil requirements.
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Then color me confused. The OP said, "I fly with an O-540," and made reference to "55 PSI (Lycoming's minimum)". He didn't identify the type of aircraft or version of O-540, though.
 
Pilawt said:
Then color me confused. The OP said, "I fly with an O-540," and made reference to "55 PSI (Lycoming's minimum)". He didn't identify the type of aircraft or version of O-540, though.
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Yes, I was thinking of a different thread!
 
What took you to redoler with such a problem? what is urgent?
 
Found the problem!

It was crud in the oil pressure relief valve. We cut open the filter to be safe and it wasn't making any metal. Sigh of relief; it flies great now!
 
SepticTank said:
Found the problem!

It was crud in the oil pressure relief valve. We cut open the filter to be safe and it wasn't making any metal. Sigh of relief; it flies great now!
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Crud in the relief valve? I'd be looking for reasons for that. Was the engine making metal earlier, and repairs made without flushing the whole thing? Or was the engine on straight non-detergent oil for a long time, then someone switched to an AD oil? That loosens a lot of varnish and carbon in the engine, including inside the oil galleries.

Symptoms have causes.
 
Dan Thomas said:
Crud in the relief valve? I'd be looking for reasons for that. Was the engine making metal earlier, and repairs made without flushing the whole thing? Or was the engine on straight non-detergent oil for a long time, then someone switched to an AD oil? That loosens a lot of varnish and carbon in the engine, including inside the oil galleries.

Symptoms have causes.
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Not to mention, the ball and seat relief valve that a Lycoming has, is not terribly susceptible to collecting trash and causing problems.

I’d be glad a problem was found but I’d investigate what might have caused the problem further.
 
Dan Thomas said:
Crud in the relief valve? I'd be looking for reasons for that. Was the engine making metal earlier, and repairs made without flushing the whole thing? Or was the engine on straight non-detergent oil for a long time, then someone switched to an AD oil? That loosens a lot of varnish and carbon in the engine, including inside the oil galleries.

Symptoms have causes.
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No metal since I’ve owned the plane (only have about 100 hours in this specific airplane) and none noted in the logs. We borescoped the cylinders and everything we were able to and it all checked out.
 
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