Gear doors not closing on gear extension.

[GAdams]

I have the same model 337 and I have had the same problem. One thing I did was to be fastidious about topping off the hydraulic fluid. Seems that bubbles can be found in the reserve. Cheap fix, but it takes many gear cycles to get out the bubbles. Of course you can use the hand pump instead of swinging the gear. You can also, with the front engine running on the ground, put the gear lever in the down position a few times and that should clear the air out as well.