Hello, wanted to ask a question... I have an X5 E53 3.0D. (04 Plate). It has the Air suspension on the rear and the "Selflevel Susp. Inact" error message has appeared on the dash and the rear suspension does not move or inflate.. when i turn the ignition on (not the engine running) i think i can hear the compressor trying to inflate the shocks, but nothing inflates... I have found a BMW X5 E53 Rear Suspension Air Bag to Coil Spring Conversion Kit, which basically a direct replacement rear coil spring kit which completely removes the old air bag suspension... Has anyone done this or basically are they any good? Many thanks in advance..

Morning Kevin

Like all rubber parts the airbags have a life (a pretty tough one under the back of an X5) There are many folks who have changed the air suspension to springs and many kits available from Motor Factors or the well known auction site, The replacement spring kits are about the same cost as replacement air bags and the air bags are really easy to change. 

My air bags failed, well one did and I replaced them both with Arnott air bags same cost as springs but I retain the self levelling for towing. Stay away from the cheap Chinese stuff springs and air bags. The old saying "buy cheap, buy twice" it isn't worth gambling with the bits that keep your car on the road (my opinion) 

So I would jack it up and listen for where the leak is, check the pipework but my bet is air bag split and as they have lasted 16 years why not replace them. Two clips one top and bottom and an air connection bit of lube sprayed on the knee joint of the sensors job done for another 16 years??? Plus it keeps my X5 original which I prefer.

If you change to springs you could strip out the compressor and sell it to recover some cost but you will still get the Sus Inactive message unless you code it out 

Dave