saggy bottom

Hi, i have read lots of posts on failing rear air suspension.

Mine has been fine but since Friday has dropped on rear near side.
it pumps up fine and i will check for leaks.

My question. i hear a whoosh of air about 30 seconds after turning engine off, from rear.

is this an overflow or part of my problem ?.

it only does it for a coulple of seconds.

thanks,

the car drops slightly after you park up drops by 20 mm i think.As for dropping on side my did this on and off for months.changed bags no prod.