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Steve M

Rear suspension drops randomly

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Hello everyone,

 

After fitting a new Aerosus compressor to my FY12 F11, I've noticed that it randomly leaks air once the engine is switched off (it's possible that it leaks air while I'm driving but I've never heard it over the noise of the engine). It only leaks for 2-3 seconds so the back doesn't drop completely, then I'll hear the compressor run for a bit a few minutes after I next start driving.

 

I had one of the bags replaced at the end of last year and it seems to drop down equal amounts on both sides, so I don't think it's them. I thought it may have been a faulty relay (I swapped the relay when fitted the new compressor) so I put the old one back in but it made no difference.

 

Does anyone have any thoughts as to the cause? I'm pretty sure it didn't happen before I replaced the compressor.

 

Thanks,

 

Steve

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On 6/11/2018 at 9:01 AM, Steve M said:

Hello everyone,

 

After fitting a new Aerosus compressor to my FY12 F11, I've noticed that it randomly leaks air once the engine is switched off (it's possible that it leaks air while I'm driving but I've never heard it over the noise of the engine). It only leaks for 2-3 seconds so the back doesn't drop completely, then I'll hear the compressor run for a bit a few minutes after I next start driving.

 

I had one of the bags replaced at the end of last year and it seems to drop down equal amounts on both sides, so I don't think it's them. I thought it may have been a faulty relay (I swapped the relay when fitted the new compressor) so I put the old one back in but it made no difference.

 

Does anyone have any thoughts as to the cause? I'm pretty sure it didn't happen before I replaced the compressor.

 

Thanks,

 

Steve

 

Hi, this is probably the normal functionality of the system. Once you park the car and open the driver's door or tailgate, an amount of pressure in the air suspension system is released to equalise the pressure in the system. Mine does this nearly every time I park it in the garage. Here's a link to the detailed description of the system including how pressure is maintained/released:

 

https://www.newtis.info/tisv2/a/en/f11-530d-tou_201007/wiring-functional-info/chassis-suspension/electronic-ride-height-control/2coth0kK

 

 

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@Matthew Ashton Thanks for your reply.

 

I may be imagining it but the ride can feel a little hard for the first minute or so of driving, until the compressor pumps the bags up again. Do you also find this?

 

I'm wondering if I should take it into to have the sensors re-calibrated as suggested at the end of the article as it seems odd that so much air is let out when I get out only to be topped up again when I next set off.

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58 minutes ago, Steve M said:

@Matthew Ashton Thanks for your reply.

 

I may be imagining it but the ride can feel a little hard for the first minute or so of driving, until the compressor pumps the bags up again. Do you also find this?

 

I'm wondering if I should take it into to have the sensors re-calibrated as suggested at the end of the article as it seems odd that so much air is let out when I get out only to be topped up again when I next set off.

 

The calibration will only set the ideal ride height but no harm in trying and it is easily done with ISTA and an Enet cable (I’ve played around with mine using ISTA). 

 

I havent noticed any hardness when driving off and off and can only imagine you’d notice it if the car was sitting on the rear bump stops so in effect no air spring at all. Can you measure the “sunk” height and the normal driving height to get a feel for how much the suspension is moving when charging/discharging? I just use my fingers between top of tyre and wheel arch and mine may drop by a fat finger measurement. 

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BMWs are designed to exacting and extreme tolerances in terms of their engineering and refinement and you use a 

 

1 hour ago, Matthew Ashton said:

a fat finger

 

to measure something.

 

I dunno.;)

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3 hours ago, 535i Andrew said:

BMWs are designed to exacting and extreme tolerances in terms of their engineering and refinement and you use a 

 

 

to measure something.

 

I dunno.;)

 

My fat finger is very scientific I'll have you know! :-) 

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