Oil pressure?

[hoskinsb]

I have searched the archives but cannot find anything regarding my particular issue. My oil pressure is at 84 psi (I have 3 washers under the ball spring) when I take off and about 5 minutes into the flight the oil pressure slowly backs down to 55 psi and after the oil temp gets to 180 degrees the oil pressure goes back up to 84 psi. I have 5.5 hours and a total of 6 flights on the airplane and it is consistent every time I fly. I am hoping for some insight before I go tearing things apart. The engine runs great and has not spit, sputtered or coughed.

RV 7 Lyc O360 with a Hartzell CS
5.5 hours SMOH
Van's oil cooler and plumbing
Oil filter
Van's oil temp gage and sender unit.

[rich]

I would first look at the oil pressure transducer.
Might be inaccurate at a certain temperature, but accurate at cold and hot.

[mahlon_r]

What was the oil temp and power setting when the oil pressure was 55 psi?
Good Luck,
Mahlon

?The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."

[hoskinsb]

I am suspect of the transducer also. Mahlon the oil temp was between 150-180 deg at 55 psi after reaching 180 deg it would return to 84 psi and stay there and oil temp also stabilized at 180 deg. MAP and RPM settings were 23-24 inches and 2500 rpm without any additional power adjustments.

Thank you,

[mahlon_r]

There are two non adjutable tower types for the oil pressure relief valve housings. A short tower cap that resembles a Bat Masterson type derby, and a tall tower cap that resembles an Abe Lincoln stovepipe hat. If you use a short tower on a crankcase that is superposed to have the tall tower, the oil pressure can drift around like that. The case that uses the small tower cap also has a cage inside the engine to keep the ball centered on the relief valve seat. The case that uses the tall tower doesn't have the cage and the tall tower cap keeps the ball aligned with the seat. When you use the short tower cap on a case without the cage, the ball can drift around and make the oil pressure weird. I would check this out, if the transducer proves to be good.
Good Luck,
Mahlon
?The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."

[hoskinsb]

Thank you Mahlon I will check it out.