[wslade2]

Check the hydraulic screen and relief ball valve for clogging.

If you’re sucking air, it can make the fluid foam. Foamed up fluid is more compressible and won’t actuate the system firmly. ie-may not get firm up operation leading to unexpected lamp indication. Foamy fluid can come out the vent. Look for hydraulic fluid on the ground under the vent or streaking under belly of plane.

I capped off my pump and hooked a hand operated vacuum pump from auto part store to the other port to check for air leak at pump. If it doesn’t hold vacuum, you’re sucking air at a worn pump shaft and bad internal seals.

If you’re on jacks, you can operate your on plane pump with splined socket from harbor freight hooked to a 1/2 inch drive drill and observe for issues.

If you unhook the lines from your pump, you can fill the intake side with hydraulic fluid (I use a hand pump oil can from tool store), then turn the prop by hand. A good functioning pump will move fluid to the output side efficiently and directly. You will see smart fluid movement without a lot of prop movement once primed. Observe for sluggish or no flow.

Look for hydraulic leak anywhere and everywhere. What wasn’t leaking before can be leaking now. I did high speed taxi this weekend to check some brake work and darn if it didn’t make a door actuator start leaking that wasn’t before.