i have no idea why i started noticing this, but my GXP seems to sag in the rear. I owned an 02 SLE before this, and i assume the rear air shocks are the same, but i never noticed that the rear shocks bled pressure like the ones on my GXP. is this something that anybody else has noticed? i always hear it after shutting the car off and immediately stepping outside to the rear. i can hear a hissing directly from the rear, and after a while the rear end sags. compressor works and all that but it just seems odd to me that i never noticed it on my 02, and by what i can tell, it shares the same rear susp components as the GXP.

mhmm, i never heard any noise when leaving mine. althought the compressor does come on for like 15 seconds everytime i start my car to lift it back up

well, my compressor runs quite a bit more than i remember it did on my sle. maybe thats the way its supposed to be. i just know that i can hear a hiss from the rear.

i never hear a hissing sound, but when i jump into my car tonight i'll time the compressor for you and i'll do the same tomorrow morning

Normal for compressor to kick on when car starts. Not normal to sag or hiss whatsoever. Check and see if you can hear where it'* hissing from. Could be just about anywhere. Leaking air shocks, couplings to them, airlines, trunk accessory Schrader valve.

the air shocks were replaced with monroe sensatracs not too long ago. its definately coming from the passenger side and driver side rear wheel well. its not sagging like an old lincoln, but the rear is definately lower after sitting for a while. the comp does kick on then shuts off after about 15 seconds when the car starts, but im positive im hearing some sort of air loss when its shut off. its not the shrader in the trunk (thats another story, mines never ever worked correctly), im spraying my air shocks and the tubing feeding them with soapy water to check for any leaks tomorrow. ill keep you posted.