oil pressure gauge needle vibrates above 2600 rpm

[rjb]

Can't hear, feel anything else odd.

Replaced my tach just because it read 200 high and I didn't want to
handwave 2900 to a DPE on my instrument checkride. That cost $400
and a week downtime, neither of which I am eager to repeat.

Anybody have horror stories or solutions about my oil pressure
RPM range needle fluctuations.

Thanks,
Dick

[maules.com]

What engine? What year?
The crankcase fitting to the oil line is restricted down or should be and maybe the hole is too big.

[rjb]

O360-C1F in N9951, November 2006 vintage

-Dick

[a64pilot]

I think it may be the gauge. The way I would approach this is to temporarily install a cheap direct reading automotive gauge. If possible use the aircraft's oil pressure line. If the automotive gauge doesn't fluctuate, you have your answer. I'm betting its the gauge itself, especially if it does it both when the engine is hot and when the engine is cold.

[RobBurson]

rjb, mine does it too at different rpm and mp. Mine flutters, fast, maybe 1/16" I think it is some type of harmonic vibration thing. If I raise or lower the rpm it goes away. Regards...Rob

[a64pilot]

Rob,
You might want to dynamically balance your prop.

[maules.com]

This pulsing was a common problem with Lycs on Maules in the '90's.
Maule brazed a restricter on the end of the angle fitting at the crankcase end of the oil line. Thus if the line ever burst, the oil could not all blow out the engine too fast and you could see the pressure drop and get on the ground.
Sometimes the hole was too big and the pulses of the engine pumped oil, would transmit to the guage.

[RobBurson]

Rob,
You might want to dynamically balance your prop.

Jody, been done. The plane feels very smooth. The only problem I see in the future is the gauge is going to self destruct. How long it takes is anybody s guess. It's not real bad, just one of those things that makes you think. Cheers...Rob