I've got an issue where the front of the vehicle sags overnight. However, if you pull the fuse it doesn't drop a millimeter. So naturally I assume all the o rings are good. Is there a chance that there's a bad solenoid in the valve block itself? I've not got a suspension fault and the rear of the vehicle raises but not the front. Maybe that solenoid is all the way gone now and won't open?

Just spitballing here but is it possible to rebuild one of these if the solenoid is bad?

 

Solenoids do burn out. Transfer case even has one that can fail. Relays contain solenoids, those can fail too. So yes, its very possible a solenoid in a valve block can fail. Generally they fail in the default state, the "unenergized" state. For the valve block, that would be were all three are closed.

 

I just went through this on the 2008. The problem was pressure rising too quickly on start up. I suspected the reservoir valve.
I put new O-rings in it, chased the galley pressure / pressure sensor voltage etc. for a few weeks and in the end I replaced it with a used LR valve.

In fact the solenoid was bad. I tore the old valve apart, put power to it and it did not move, so I figure I got it right by replacing it.

hope this helps

Jeff