"hydraulic lock"

[wpoplo]

My 912 after sitting a while(three weeks) gets what I call a "hydraulic lock", engine oil gets into the right rear piston head area and will not turn over until I pull the plug and drain the oil. Could a person redesign the oiltank and lower it down on firewall to keep it from draining into the engine? Any advice would be appreciated.

[Av8r3400]

What model kitfox is it?

Update to the new Rotax oil filter with the internal check valve will help eliminate the problem.

[wpoplo]

It is a Model 4 that I bought in Nampa, Id from Skystar. The SN is 132. The engine is a 912A??

[HighWing]

[QUOTE=wpoplo;31825Could a person redesign the oiltank and lower it down on firewall to keep it from draining into the engine? Any advice would be appreciated.[/QUOTE]

Pat,
I know of one owner who moved the oil tank to a position lower on the firewall. Mine is lower, but I moved the engine for W/B that created a little more room. I would suspect the left side might be the best side - I can't remember where my friend put his. His had straps that mounted the tank to the firewall rather than attaching it to the engine mount.

I have looked long and hard over the years for a taller more slender tank from the Motorcycle ranks that would fit better. For some reason, they all seem to be pretty much the same diameter. I have also thought of having one welded up in a custom shape but never followed up on that idea - round has some definite disadvantages fit and location wise.

[kitfoxflyer]

HI i on my model experienced oil draining from the oil tank into the engine sump
on my model 1V1200 rotax 912,I installed a ball cock between the oil tank and the oil cooler and turn it off at the end of each days flying. it has fixed the problem. I attatched a micro switch to disengage the starter solenoid so that it could not start with ballcock in off position, this was also connected to a warning light and buzzer in cockpit. In the on position it was fitted with a locking device so that it could not work into the off position during flight.

[wpoplo]

Thanks for your information, I am still taking dimensions on the right side of the firewall trying to make a rectangular oil reseviour(sp) there.

[Av8r3400]

Keep in mind that the Rotax oil tank has specific reasons for its design.

The way the return line goes in combined with the screen reduces foaming. The screen is not a filter. It's there to combat foaming.

I have the exact same fwf on my plane, and with the use of the proper filter, I have never had any issues. Why reinvent the wheel?

[DesertFox4]

Hydraulic oil lock has been with us since the very first 912 was installed on a model 3. It is not new and is easy to live with if proper procedures are used before starting your engine for the first time each day.


I agree with Av8r3400. The oil system on the Kitfox is tried and proven. The shape and size of the oil tank is integral to the proper function of the oil system. Reinventing the oil tank could lead to unexpected consequences as could installing shut off valves in the oil lines. I would not recommend either approach.
The new oil filter from Rotax is designed to reduce this condition. It has helped using the new Rotax oil filter. I still, out of habit, pull my prop though many times before starting the engine after the aircraft has sat for a period of time to make certain no oil has gotten into the cylinders.

P.S.- never pull your prop in reverse direction to engine rotation to clear oil out of your cylinders.

[wpoplo]

What has Rotax done to make the oil filter stop hydraulic lock?

Thnx
Pat

[Av8r3400]

The Rotax filter has an anti flow back valve to prevent hydro-locking in it as well as the appropriate pressure relief valve.

The NAPA and other brand filters are different. They are designed for industrial engines, not the special needs of a Rotax aircraft engine. Just because it fits, doesn't make it right...