i would like to thank kiwi for the pictures of DIY air spring of Arnotts i just did mine last firiday . i had my left side sagging or lowered for one month until the right side got affected as well. i followed the procedure and the toughest parts after removing the plastic covers of both sides were the pins inside ( gold color) around the tube and the clip at the bottom of the air spring. it took me 2 hours but a the end it it was worthwhile instead of being robbed $900 by the dealer. the only isssue is the car did not level up. i took it to the dealer on friday for the cause and today i was told it was the vertical sensors that need to be replaced and i talked to the tech myself and he was schocked after telling him that i myself changed ther air spring . he concurred that the air compressor was fine and the ait springs are fine and the sensors are the issue.
parts # 2[(37-14-6-784-697), (37-14-6-752-797) and the price to put those is $ 737.88 before tax i believe. i will purchase the parts at bmwmercedesparts.com and try to find some one who has the tool to recalibrate the height.
NB: any x5 owner should educate yourself about your car cause there are lots of stuff that can be done without the intervention of the dealer.