Landing Gear Dump Valve

This airplane has had a problem since they day I got it.  The landing gear hydraulic pump would cycle rather often to keep the pressure up in the system.  On the gear up side it would rarely bump the pressure up, maybe once an hour.  On the down side the problem was getting worse.  The pump would bump about every 30 seconds.  Talk about annoying..

For starters, most of the hydraulic lines in the gear system didn’t look good at all, and were starting to leak externally.  I replaced all of the hydraulic lines thinking I was going to fix the problem.  Not so..

Now that I didn’t have any external leaks (but the pump kept bumping the pressure) I started to rebuild the actuators.  It could have been any of the 3 gear actuators or any of the 3 gear door actuators.  All of them got new seals, including the sequence valves.

Still not fixed..

At the time the only other thing I could think of was the pump itself had an internal leak.  Soooo replaced the O-rings in the shuttle valve.  See photo.

Still not fixed

The very last idea was the dump valve leaking pressure from one side to the other.  I took it apart and sure enough, you can see the seal displaced inside the ball valve.  Plus, this valve isn’t rated for anywhere near what the gear system pressure could be. ~1500 psi

I replaced the valve with a Parker unit that was about the closet fit I could find, for a whopping  $11.  The cheapest part in the entire system was the problem.  Go figure