Air Suspension Deflating

[kougarman]

Can you help? I drive a 2007 E70 30d SE (80K miles) and sometimes when I go to the car in the morning, the back suspension has deflated over night.  As soon as I unlock the car,
immediately the pump starts and brings it up to its proper operating height and then the suspension stays inflated all day. It seems to deflate overnight but this doesn't happen every night, the fault is intermittent as some mornings the pump is silent and the suspension is up.  I am concerned about wearing out the pump and its high cost of replacement.  Has anybody experienced this fault and have any ideas what component could be failing?  After the last service the indy advised that the "rear air springs outer casing are starting to fray"  but that shouldn't deflate the suspension.  Any thoughts would be greatly appreciated.

[Graeme]

First, can I assume you're parking it on the same  level surface each night as variations in the ground can lead to a different look.  With the car on level ground overnight, and before starting it up, measure the distance from the top of the wheel arch to the centre of the wheel hub. They should be very similar on each side.

I had a similar issue about 4 years ago with my car which is of the same age as yours, and mileage the same then. My indy mechanic put the car on a ramp and with the wheel off on the offending side and a jack lifting the hub to compress the air bag, the bag was sprayed with soapy water.  Immediately tiny bubbles appeared where the bag folds when compressed - they're made of a rubberised canvas that clearly deteriorates where the material is flexed time and time again.  Only cure is to replace the bag. Mine came from Europarts and there are U-tube videos showing how straight forward it is. Since then the other side was done about 18 months ago!

I'd suggest getting it looked at ASAP to ease the load on the compressor - which is a lot dearer than an air bag!  BMW will charge a lot more than indy garages for the job that does not need any coding done afterwards.

[kougarman]

Thanks for your reply.  Yes, parked on level drive over night.  I'm just going to have to "bit the bullet" and get my indy to replace both sides.  Looked at the YouTube video and as you say, fairly straight forward. Better this than a new pump! 

[Graeme]

Indeed!  Though you may not need both sides replaced - just the defective one.  However, I'm sure your mechanic will want to test both sides with the soapy water technique!

Best wishes,

Graeme