MB164

Hi, just joined today. Glad to be a part of MBWorld. Have a W164 year 2007 which has just started to give me some air suspension prob. Every time I park I notice drivers side suspension dips down. There is a click and air is released. Sometimes when the car is raised to off-road level 1 and switched off it remains up. Mechanic told me that i need to replace the suspension for the drivers side but I can't buy his story coz doesn't explain the fact that it remains up sometimes. Afraid that this will ruin the pump next. Pls help.
:confused