[Piper J3]

Rotax requires that you purge air from the oil system if you break loose a hose connection or perhaps changeout the oil cooler radiator. My question is… when changing the oil filter, is it necessary to pre-fill the filter so air is not introduced in the oil system (hydraulic lifters)?

 

[Bob Y]

At the Rotax school, Lockwood recommended partially pre filling the filter. Attached are my notes on their recommended oil-change procedure. See step #4. The only thing I do differently is the oil-filter tightening step. Call me anal, but hand tightening just doesn’t seem adequate, so I go with the Rotax recommended 3/4 turn. Lockwood said this process should eliminate the need for purging.

 

[seagull]

I have done approximately 30 oil changes (50hr in between) on my engine. From reading Bob’s notes I have missed a few things. I always change after a flight so oil is at operating temp. I do let it drip until it stops, 30 min or more. I prefill the filter about 1/2 and let it soak into the element before installing. Hand tight plus 3/4 with wrench. I have never pulled it through afterwards, just start. I am not suggesting this method just what I have done without issues

 

[bobg56]

I will add this, before draining oil burp the oil tank so that you get all the oil out of the crank case. Even after shut down there is still some oil that needs to be returned to the tank.