Hight oil PSI

My o-320 as started showing high oil PSI(90-100) at anything over about 2000rpm.
I checked it with a mechanical gauge just to make sure, same readings. Filter and oil change about 6 hours ago, used same oil 100W. Any ideas ?

Skip RV-4
o-320 b3b

Pressure relief valve?

Check your pressure relief valve. Not sure which style you have, some are adjustable, but if yours is like mine its all mechanical with a steel ball and a spring. Pressure is regulated via spring pressure and a combination of washers that will either increase pressure (more washers) or decrease pressure (less washers). I would take it out and inspect it for damage, carbon ect... May also want to run a piece of safety wire from the drain hole down to the sump to ensure nothing is clogged. Assuming you have a Lycoming, it should be located on top of the RH aft cylinder #3. There is info within the VAF brain trust on this as well as the internet search would help.

egp8111 said:

My o-320 as started showing high oil PSI(90-100) at anything over about 2000rpm.
I checked it with a mechanical gauge just to make sure, same readings. Filter and oil change about 6 hours ago, used same oil 100W. Any ideas ?

Skip RV-4
o-320 b3b

Click to expand...

Did you have many 10's or 100's of hours at a lower pressure? If that is the case, that is concerning. I can't think of a lot of reasons for that to happen, outside of mechanical issues with the relief or blockage of the drain back port at the relief. The pressure relief shouldn't just get tighter overnight. I would not bother adjusting it, but pull it off and looking for a mechanical issue that is applying more spring pressure to the ball.

Larry

I have the same issue with my O-320. Pressure goes above 90 psi after a few minutes of flight even with engine back to 2200 RPM. And that is also after a recent oil change.

If I land and shut the engine off for a few minutes, then restart, oil pressure seems to go back to normal for the next flight segment.

Not sure what is causing this. Anyone any ideas?

Phugoid said:

I have the same issue with my O-320. Pressure goes above 90 psi after a few minutes of flight even with engine back to 2200 RPM. And that is also after a recent oil change.

If I land and shut the engine off for a few minutes, then restart, oil pressure seems to go back to normal for the next flight segment.

Not sure what is causing this. Anyone any ideas?

Click to expand...

Failing pressure sensor

What style relief valve cap do you guys have? One that looks like a Bat Masterton derby? or a Abe Lincoln top hat? or the adjustable type with a screw adjustment out the end? If the first style, you could have a missing steel cage in the crankcase that keeps the OP relief ball centered on the hole in the crank case. This cage is not there for the other two styles of caps as those caps perform the function of centering the ball. This lack of the cage with the short derby style cap can allow the ball to seat irregularly and can cause oil pressure to vary greatly from flight to flight or even during a flight and then be totally stable for a period of time. Just depends on how the ball hits the seat with no centering device to align it perfectly. Maybe not applicable, but something to check.
Good Luck,
Mahlon