Shocks or springs?
 

Ok i have a 2000 DTS, the car levels up when i start it, no problems. Driving the car it stays leveled, no compressor on or anything. The second someone gets in the back seat it drops and sags, compressor comes on but cant sustain the load. If it was a leak wouldnt it just sag all the time? When the car is off, i can do the bounce test on the car and the rear bounces more than it should. Do you think its the shocks or the springs? Also doesthe front of the DTS have leveling also? I actually found a set of air shocks off a dts that was wrecked for 60 bucks> i just want to see if they may be the problem. Thanks

Problem should relate to air shocks, lines, or compressor operation. Compressor should power up when car is started for 1-3 min. If it doesn't, that could be your problem.

it powers up, but when the load is heavy it cant raise it, it just drops