I thought maybe the diaphragms were going out because that pump runs all the time, and gets especially noisy in the summer. Noise increases on really hot days. I thought something was going on where it was having to work really hard at leveling the suspension. Maybe the hydraulic fluid level is low. Hm.
Could the pump noise be the fuel pump dealing with evaporated gas in the fuel tank? (More evaporation on hot days?)
The ride is fine, and the rear end seems to behave over bumps. I have driven other 300TE wagons with fewer miles, and the ride in my wagon seems comparably good.
Thanks for the feedback.