Suspension issue immediately after MOT??

[Rapid85]

Hi All,

My car went in to a local Indy last week for MOT/Oil service. All good. But immediately after getting the car back, when left overnight, the suspension is down at one side. A classic air bag problem I imagine, of which I've had issues with for this car before.

Whilst I might put the timing of going to the garage down to pure coincidence, this happened when it went there before a few years ago! (and in fact I did put it down to coincidence the first time) When I had the issue before, it all started the day after it went to that garage. I think from memory, it was an MOT the previous time too.

What on earth could be going on here? Is there anything in the MOT procedure that could explain this? The suspension was perfect on both occasions before going to this garage.

The garage has an excellent local reputation and I've found them good for fault finding, mechanical knowledge and service in the past. There's just no way this can be coincidence.

I'm obvious going to call them but I could really do with some background knowledge of what it could possibly be before calling them, as it's difficult for the call not to come across as an accusation.

Thanks in advance.

Edit: having checked records, said air bag was replaced just over 1 year ago, and really shouldn't be an issue.

[TwinKam]

What's the car? And is it the same side as the one that failed before?
During the MoT, when the suspension is checked, all the wheels will go to 'full droop'. Whilst this in itself shouldn't cause any problem (it will obviously happen when any corner is jacked up to raise the tyre off the ground), it is a position that a car doesn't experience everyday but one that yours has on both occasions just before you say a bag has 'failed'...

[Rapid85]

Yes sorry, the car would help. It's a 2014 BMW 730d and yes, it is the same side that failed, although I had both bags done the time as it seemed the other side may have been slightly effected. Due to the age of the bags I figured I may as well get them both done at the same time.

I do trust the garage so for now, if we're going with the theory of it being in that infrequent position that could be contributing to the issue, what could possibly cause that?

Thanks for your help.

[Smint]

As above, when lifted the suspension will probably go an angle it never normally sees, shouldn't affect an airbag unless its on its last legs and splits open, but the height sensor itself or its linkage might be corroded or sticking...not sure what system is used on BMW, i'm going from similar known issues with Toyota 4x4's with rear air and the headlight self adjuster linkage/controller on Subarus with self leveliing suspension (not air), Toyotas its usually corrosion in the height sensor itself, on Subarus the linkage (think of a minature suspension drop link) actually seizes solid and the support bracket eventually breaks.

[Rapid85]

Smint said:

As above, when lifted the suspension will probably go an angle it never normally sees, shouldn't affect an airbag unless its on its last legs and splits open, but the height sensor itself or its linkage might be corroded or sticking...not sure what system is used on BMW, i'm going from similar known issues with Toyota 4x4's with rear air and the headlight self adjuster linkage/controller on Subarus with self leveliing suspension (not air), Toyotas its usually corrosion in the height sensor itself, on Subarus the linkage (think of a minature suspension drop link) actually seizes solid and the support bracket eventually breaks.

Thanks for that. When I say the it's down on one side, I mean the arch completely sunk into the tyre effectively, so not sure if a height sensor could be an issue?

The first time it happened, assuming the bag hadn't been changed before, it will have been around 8 years old, so quite possibly going full droop could finish it off. The current bag is 1 year old and about 10k miles. You wouldn't have thought that would be on it's last legs, unless it's defective somehow.

[MustangGT]

Where did you source the replacement airbag? Was it a genuine replacement part or cheap off eBay?

[Rapid85]

MustangGT said:

Where did you source the replacement airbag? Was it a genuine replacement part or cheap off eBay?

Yes it was a cheap replacement part on Ebay, although the mechanic did tell me it seemed really well made when he fit it.

BMW or similar don't make them, they just do the entire strut at a cost of 4 figures. So these cheaper aftermarket manufacturers were the only options, as they're the only sort that make the bags separately.

[paintman]

That might be the problem.
I bought a pair of cheap droplinks from ebay for Mrs p's Pug 307.
The rubber boots split within a matter of months.

Edited by paintman on Tuesday 7th November 12:04

[jfdi]

If your not going with oe airbags then Arnott is the only real other choice worth considering. Cheap airbags are cheap for a reason.

[Rapid85]

I don't think Arnott make them either. They only due the whole strutt, from memory.