Land Rover Repair: air suspension problems, airsprings, air reservoir

Question
I own a 2000 range rover hse. The suspension has been acting up for few months now. It sometimes lowers over night and other times it does not. When it lowers half the time it happens from the rear only.  Sometimes it lowers immediately as soon as I park and usually I can hear the air coming out. It takes a long time to rise after it has been down and usually it is slower to rise when the weather is cold.  Any help in diagnosing the problem is greatly appreciated.

Answer
This is most likely leaky airsprings.  They can leak at one height but not another, cold temperatures make the leaks worse.  When the system leaks down overnight it tends to also drain the air reservoir, which helps cause the slow rising in the morning.  New springs and a compressor rebuild are in order at a minimum.  A valve block rebuild will help as well, but isn't as necessary.