Oil pressure/Prop Gov issue

[Robert Hicks]

Greetings,

 

So I’m putting the finishing touches on my overhaul and some general updates on the airplane. Today I went to take it for it’s first flight and had an issue. On startup and down to the run up area my oil pressure was ~80. I perform a run up, all is well until I cycle the prop. Oil pressure drops to about ~55 and never returns to ~80. I bring the rpm back to 1000 and the pressure goes up to ~60. If I add throttle the pressure drops back to ~55. The prop reacts immediately and rpm returns etc... Just oil pressure. Temp is showing ~160 during this. I have an 8 hour snew prop and a pcu5000 governor.

 

Any thoughts?

[carusoam]

Expect lots of air in the system..?

Gear pumps, we have two... are pretty good about pushing air through the system...

But, if they are really dry... they may have additional challenges...

Oil pressure is set via a regulator at the end of the oil gallery...

pre-filling the system is probably a really good idea...

Was there an oilP setting procedure to go with the OH?

PP thoughts only, not a mechanic...

Best regards,

-a-

[Robert Hicks]

Thank you for the reply. And yes I’m beginning to think there may be an air bubble in the system somewhere. Lycoming instructions were followed when filling and oiling the system per the manual.

[EricJ]

Check your oil level first.   If that's okay, if you haven't cycled the prop a bunch of times, do it several times (like a bunch) and see if it makes a difference.    Even if there's an air bubble in the hub, it shouldn't affect engine oil pressure, so something else might be up, too.

 

 

[carusoam]

Find the oil pressure adjustment... see if it somehow came loose.. Or moved?

It may be called the oil pressure relief valve...

PP guess only...

Best regards,

-a-

[carusoam]

11 hours ago, Robert Hicks said:

 

Greetings,

 

So I’m putting the finishing touches on my overhaul and some general updates on the airplane. Today I went to take it for it’s first flight and had an issue. On startup and down to the run up area my oil pressure was ~80. I perform a run up, all is well until I cycle the prop. Oil pressure drops to about ~55 and never returns to ~80. I bring the rpm back to 1000 and the pressure goes up to ~60. If I add throttle the pressure drops back to ~55. The prop reacts immediately and rpm returns etc... Just oil pressure. Temp is showing ~160 during this. I have an 8 hour snew prop and a pcu5000 governor.

 

Any thoughts?

 

I’m thinking it would be really helpful to know which engine we are discussing...

Consider writing it in your avatar area...

plane, location, add a pic... the usual...  

Best regards,

-a-

[Robert Hicks]

It’s a 63c model with an O-360-A1D. The prop has been cycled many many times. I have 7 quarts in the engine and no leaks. I think the air is in the case somewhere. Lycoming operators manual suggests that as well for low oil pressure. Next weekend I am goin to check the pressure at the nose and see if I’m within limits.

[Prior owner]

My thoughts:

What are the oil pressures at 1800 rpm before the first time you cycle the prop and before the last time you cycle the prop with warmed up oil?

Higher engine rpm causes a greater volume of oil from the oil pump. This means that you should get an indication of higher pressure with higher rpm in a warmed up healthy engine provided there is no excessive wear in the engine. While it is possible for an air bubble to develop in your prop or oil cooler, an air bubble developing in the engine is highly unlikely.... All things being the same (this happened suddenly and is not related to higher OAT/oil temp, you have the same oil type as before,  and you have no external oil leaks), you’ve either got an issue with the oil pressure gauge/line, the oil pump, a clogged oil pump pickup, an internal oil leak, a restriction in the system between the pump and the pressure regulator, or an issue with the oil pressure regulator not operating correctly or having something lodged in it.
 

What other maintenance was performed recently?

 

Try the simplest Things first- loosen the connection at your cluster gauge for the oil pressure gauge a little, run the engine with a rag or cup under it, and allow it to bleed off any air that might be in there. Not my first guess as to what might be wrong, but the easiest to rule out. 

[carusoam]

Verify the OilP reading first...

For the old mechanical gauges.... they have a procedure for proper gauge set-up... how much of an air bubble in the line...

FuelP gets this as well... 

Often there is a calibrated restrictor in the line near the gauge... to help minimize instrument needle bouncing with pressure oscillations...

Great details added, Robert! Thank you, that helps a ton...  

Best regards,

-a-

[Robert Hicks]

5 hours ago, PilotCoyote said:

What other maintenance was performed recently?

The entire engine was rebuilt.. Lol. Seriously tho, all brand new parts less the case and crank (overhauled).

[Prior owner]

Oh, I misunderstood...I thought it was your prop that was overhauled, not the engine... 

[Don Heene]

Pull off the oil suction screen between the firewall and the engine it might be clogged.  

[Robert Hicks]

30 minutes ago, PilotCoyote said:

Oh, I misunderstood...I thought it was your prop that was overhauled, not the engine... 

No worries. Engine is new, prop has 9 hours on it.