Gerard,

I have pressure gauges on my 360. I have not noticed a tendency of the high pressure to increase because the temperature is usually cooler at altitude, and the pressure usually decreases a little during a flight. However, I have noticed the low pressure increasing over time, especially after a flight at altitude in the cooler air when, after landing, the plane sits in the sun on a warm day. Initially, the low pressure will be 500 psi, but as the fluid warms up, the pressure may go as high as 900 psi or more. What is interesting is that my pressure relief valve is set a little under 600 psi, maybe about 560 or 570. I have checked this many times when adjusting the low pressure switch (set the switch above the relief valve setting and the pump will run continuously revealing the relief valve setting). Apparently, the relief valves behave differently if the pressure is increased gradually as compared to rapidly.

Mike Reinath
LNC2 at 450 hrs TT
San Jose, CA (RHV)