To anyone who has had this problem or knows of the solution:

A couple months ago my hydraulic pump began cycling often, like every 15 to
20 seconds for a brief half second burst, in cruise at altitude, i.e. 85 or
9500 ft.  It seemed to be altitude related, that is, the pump would begin
cycling as I climbed above about 6000 ft.   Previously, it would never cycle
even over an hour or more leg.

1. I ordered from Lancair, and installed, a new dump/bypass valve.  The
symptoms/cycling continued.

2.  I ordered and installed a new high pressure hydraulic switch.  The pump
cycling continued.

There are no leaks, the reservoir is full.  There has never been any cycling
on the down side.

Today, on another flight to get it to do something, it did something.  At
9500 ft. in cruise, the short bursts of pump cycling got more frequent, then
the pump started running for longer periods of time, then it came on and
just continued running.  I listened and watched and after about 20 to 30
seconds pulled the circuit breakers (pump and relays).  The gear did not
drop out of the wheelwells.  I descended and prior to landing, put the gear
switch down then pushed in the relay and pump CB's.  The gear came down
normally, three green, the pump turned off and did not cycle at all all the
way in to shutdown.

I'll get it up on jacks and try to sort it out.  But in the meantime, can a
hydraulic guru tell me if this problem is internal to the pump maybe?  Do I
need to replace the pump?  If one of the actuator seals is shot the pump
would cycle on the down side, right?  Also, if an actuator seal is blown,
the gear would fall out of the wheelwells with the CB's pulled, right?

So, what is going on here?

George Shattuck
N320GS