Had this problem early on in my 235 as did another 235 flyer at the same airport. I replaced the sequence valve, carefully readjusted the valve actuator, etc., etc. without much success - still happened on accasion. After much fiddling, we both cured the problem by re-bleeding the hydro lines and cylinder for the nose gear door. I have no idea why this would have caused the out-of-sequence operation of the door or why bleeding helped, but it hasn't happened again in over 10 years. Go figure.

If any of you hydro system gurus out there can come up with an explanation, I'd sure be interested.

Dan Schaefer
LNC2     N235SP