Purging 912ULS

[Agfoxflyer]

After 5 year rubber replacement I tried purging the oil system. Put 10 psi on system All spark plug wires removed, one spark plug each cylinder removed. After many turns of prop the oil pressure gauge went up to 10 psi then dropped back to 0 immediately . Then nothing. Oil tank full. Any ideas?

[Dave S]

Dave,

Only thing I could think of is the possibility of having a big slug of air behind the oil that initially raised the pressure before dropping off. Considering the the oil filter and all the hoses, plus possibly the oil cooler are empty it might take a lot of rotation to purge it all out. I'd adjust the air pressure on the oil tank to the max allowable and then hand prop it for an extended number of rotations.

[Dusty]

Loosen the filter and hand prop until oil is pushed out around the seal.
This reduces back pressure and makes initial purging easier

[efwd]

The process involves disconnecting the oil return line from the oil tank and pump oil into a container. If you don't your just pressurizing everything and the oil doesn't circulate as it should during the purge process. Unrestricted on the return.

[Agfoxflyer]

The process involves disconnecting the oil return line from the oil tank and pump oil into a container. If you don't your just pressurizing everything and the oil doesn't circulate as it should during the purge process. Unrestricted on the return.

I did have oil coming out of return. The oil gauge never showed pressure consistently. It did last time I purged. Maybe oil pressure gauge is bad.

[Slyfox]

10psi seems low. I use shop air with a quick blast into the vent line while cranking the motor.