2008 4.8i - Rear end drops within 24hrs.
-Replaced both rear bags = no difference
-Replaced air valve solenoid = no difference
-Inspected air lines - no leaks found
-Inspected air inputs at bags, air valve solenoid, line from compressor to air valve solenoid all was well but I teflon taped, re-installed, then used liberal amounts of high heat silicon... still the back end drops.

Next up air compressor? I read somewhere that the rings on the pistons of the compressor may wear out overtime and leak. I thought that would only hinder the performance of the compressor but was not aware that it could also cause the air holding up the bags to escape. Thought that is what the air valve solenoid was for.

Any other ideas? :dunno:

A bad compressor wouldn't cause the bags to sag though. That's what the solenoid is there for isn't it? (just trying to think a loud)

It feeds the air, the solenoid opens to allow the air to pass through and once complete it would shut off closing any air from surging back to the compressor. That's why when you want to release air you undo the lines at the solenoid. When you undo the air line coming from the compressor nothing happens (back of the solenoid - black air line).

Also how are you checking for leaks? Best way is to submerge into a clear container filled with water.

I inflated the bags with just a regular air compressor used for tires and dunk them into a clear plastic tank to make sure there were no leaks.

Also are you using Arnott bags? Even if their fittings are push in fittings, I did tighten mine another 1/4-3/8 turn.

The new air valve solenoid is Arnott but the bags are not I'm affraid. They were from China and seem decent quality but perhaps not enough. I will take them off and inflate+ dunk.

The fittings screw into the tops. I used teflon, then tightened by hand then another 3/4 turn followed by silicon sealant.

I'm getting pretty good at removing them by now lol!

I did the same exact thing, minus the silicone sealant and still had leaks. The Chinese bags are super inferior compared to Arnotts.

Thanks for the advice! :thumbup:

Also my Arnott solenoid was faulty from the box. I swapped back to stock solenoid with Arnott bags.


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Just wanted to update on the latest on my issue.

Took the car back to the independent garage who fitted the bags that I supplied - they said that the left bag is faulty and air is leaking from the top where the connection is made (All I got told!) no offer of trying anything else.

Whilst I was there they looked at another issue - which is that the car has a wobbling sensation through the steering wheel at 60mph. This has been diagnosed as both suspension arms.. approx £750 to replace!

I'm almost at the point where it would be more economical for me to trade the car in. I've spent £1,200 and still finding issues!

I have the car booked in for a second opinion next week so will update with what they say.

If the arms are bad (actually it's probably the bushings, not the arms themselves), those are super easy to replace, cheap, even if you use high quality parts, assuming you are comfortable with DIY.

+ 1

@mkelly21 - over time, repairs start adding up (and will continue to do so), my experience is that doing anything* at the dealer is $$$$, on a good shop** a bit cheaper and DIY*** saves you labour or gives you room for better parts.

*-some stuff is only possible at the Dealer or you may want to let them do it due tools/expertise
**-shops can be cheaper but you still need to buy parts which are more expensive comparatively
***-DIY can save you a lot of money on repairs and maintenance that can be performed fairly "easy"; now this depends on having the tools, time, a place to do it and most importantly -IMHO-, in enjoying the process (really, if you don't like fixing stuff, it won't help - not meant to imply anything BTW - just my personal opinion, sometimes seems my BMWs like to keep me busy - LOL :rofl:).

Cheers,

I haven't heard or seen much about the rear spring kit to replace the bags.

Can anyone provide any feedback?

Thank! :)