Whats normal top off/refill of hydraulic fluid (337B)?
 

I seem to be losing fluid from the overflow vent.
Within 3 flights i had to topoff about a quart of fluid.
Whats considered normal?
If this isnt normal, what would cause this?

Check maintenance manual
 

There was one condition where the system spits hydraulic fluid out over the side,
and it won't leave a stain UNLESS it happens to hit the pilot side gear leg in flight.

The fix was minor, the condition in the maintenance manual somewhere under landing gear.

Did you find out why your loosing fluid ?

Im in the process of testing. the fill screw was missing, im thinking that could have caused an issue. plugged it back up yesterday. ill report back.

Be aware of air in the system which can cause the fluid to foam up and overflow.

yes. i did experience this when the nut on the elbow going into the rear hydro pump was loose and the threads wore out. it created a venturi situation and hydro fluid foamed out of the vent. took a while to find/understand what was happening.

anyway, this is different.

i have flown a couple times and it seems top off is minimal now. signs pointing to missing hydro fill screw causing the issue.

Looks like the fill tube goes to the bottom of the reservoir. If so, missing that nut leaves tube open to a high pressure area from ram air. Can pressurize reservoir and possibly even bubbles the fluid introducing air or even foaming.

See attached link
Tube #68