One more air suspension Q

[nuggetman]

I was late to the party in realizing my bags were dying and recently followed the guide to replace the airbags & compressor (yes, I killed it) here: https://f15.bimmerpost.com/forums/sh....php?t=1511949

I discharged & refilled the bellows via ISTA without issue but now the ride height is low and the compressor never kicks to top the bags up. I tried the ride height calibration and the sensors are showing 701mm/704mm height in the rear left/right sides which are the same values I get when measuring manually with tape.

Fuses 110 & 135 are new. I have tried unbolting and manually moving the rear level sensors and that doesn't seem to do anything, which makes sense as they should have already done their job and caused the compressor to top up the bags. I have also tried disconnecting & reconnecting the compressor and the level sensor plugs and still no joy.

Only other thing I can think of is that despite reading the values properly the sensors are somehow bad and not telling the compressor to kick in. Is there anything else to be done or tested other than replacing the sensors?

[CatalinP]

Have you tried going for a short ride?

[nuggetman]

Yes, have been driving around with it like this for a few days now, just being cautious not to load the car up!

At this point the only parts I haven't swapped out are the sensors & the control module, am guessing I would see a code for a module issue.

[nuggetman]

Ordered new sensors, hoping it's not the control module.

[F15_SGM]

What compressor brand did you install also did you transfer any parts from the old compressor to the new one? I don't think it's any module issue or sensor if everything worked prior to the replacement. Have you tried the old compressor and see if it fills to the same height? The main thing anytime you disconnect the compressor always install a brand new relay. This is a must. Autozone sells them locally if you want to try that.

[nuggetman]

Yer, the old compressor was waterlogged & blew the 40amp fuse after I tried the desiccant change trick.

The new kit came with a relay, I bought the whole assembly from Miessler automotive after I couldn't find an OEM in stock: https://www.miessler-automotive.com/...-37206875177_1

I can drain & refill the system with ISTA (tried again today) so I know it fills ok and it has held the same height for days. I also ran the compressor test today & it ran for 20 seconds after ISTA told it to.

ISTA says the nominal height value should be 734mm rear and the sensor is showing it as low but the "system" isn't doing anything about it being 30mm low. If I understand it correctly the EHC is the brain that should care that the rear is 30mm low.

[F15_SGM]

Originally Posted by nuggetman

Yer, the old compressor was waterlogged & blew the 40amp fuse after I tried the desiccant change trick.

The new kit came with a relay, I bought the whole assembly from Miessler automotive after I couldn't find an OEM in stock: https://www.miessler-automotive.com/...-37206875177_1

I can drain & refill the system with ISTA (tried again today) so I know it fills ok and it has held the same height for days. I also ran the compressor test today & it ran for 20 seconds after ISTA told it to.

ISTA says the nominal height value should be 734mm rear and the sensor is showing it as low but the "system" isn't doing anything about it being 30mm low. If I understand it correctly the EHC is the brain that should care that the rear is 30mm low.

The air block on the compressor is something you should try and switch with the original air block. Sometimes the non-OEM air block doesn't work properly. Then I would try sensors or EHC since the fuse kept getting blown. The rear links should also be checked if it's damaged. The links control the maximum psi to fill automatically.

[nuggetman]

Got it, will work my through way through and report any findings! Appreciate eveyone's help.

[nuggetman]

Following up on this in case anyone else has this issue, I replaced the EHC control module, flashed it with ESYS, calibrated sensor height using ISTA. After a power off & startup the bags filled back up and right is proper.

Thanks for the tips and a shout out to everyone on this forum for all the DIY guides that have saved me a boatload so far!

[TheUltimateDrivingManiac]

Replaced the air bag, car still sags. Happens sporadically. Car raises back to normal in 15 seconds after the start. Any ideas what else that can be?

[F15_SGM]

Originally Posted by TheUltimateDrivingManiac

Replaced the air bag, car still sags. Happens sporadically. Car raises back to normal in 15 seconds after the start. Any ideas what else that can be?

Depend on when it sporadically drops? Does it drop when parked? Driving over rough roads? etc. If it releases pressure when parked overnight and the compressor fills it back up every time then it sounds like a leak somewhere.

[TheUltimateDrivingManiac]

Originally Posted by osmansiddiqui95

Depend on when it sporadically drops? Does it drop when parked? Driving over rough roads? etc. If it releases pressure when parked overnight and the compressor fills it back up every time then it sounds like a leak somewhere.

Yeah, only when parked. OEM spring replaced by a dealer. So either they did something wrong on it’s an air tube slowly leaking 🤷*♂️

[F15_SGM]

Originally Posted by TheUltimateDrivingManiac

Yeah, only when parked. OEM spring replaced by a dealer. So either they did something wrong on it’s an air tube slowly leaking 🤷*♂️

Both sides leak or just one side?

[TheUltimateDrivingManiac]

Originally Posted by osmansiddiqui95

Both sides leak or just one side?

Just one side, right - spring was replaced yesterday, but still leaks. Another air spring, left, was replaced a year ago without any issues.

[TheUltimateDrivingManiac]

Actually… Now it’s both sides It was just a right side before the spring was replaced

[F15_SGM]

I think the compressor needs servicing. First I would try a new relay. My setup of air spring was just like yours. I had the left side new and the right side old. Until it started leaking on the right. I had it replaced as well but the same issue started as your X5. Although you should check the lines with soap and water for leaks. Air suspensions you have to diagnose 1by1. It's also possible the tech did not insert the airline correctly as you just had it replaced barely 2 days ago.

[TheUltimateDrivingManiac]

Thank you! Sent it back to a dealer yesterday, will see what they would say. I’m 90% sure they installed something wrong.

[TheUltimateDrivingManiac]

Well, as I expected, the dealer found nothing. Car still sporadically goes down though. Found this great video that explains the problem:

Will try to replace valves before replacing the whole compressor, which so far works great and get the car back up in no time.

[Mavsfan]

Originally Posted by TheUltimateDrivingManiac

Well, as I expected, the dealer found nothing. Car still sporadically goes down though. Found this great video that explains the problem:

Will try to replace valves before replacing the whole compressor, which so far works great and get the car back up in no time.

Did you try replacing the solenoid valve, and did it fix your problem?

My car kept sagging down last year, and I had the bags replaced by an indy shop. Worked fine for a while, then was slammed a few days ago. Turned the car off, left it for a while, unlocked the doors and it rose all the way up. Drove it home. Next morning, it's still up high. Drive about one block, and it slams down again. Took it back to the indy shop that says the bags are fine so it must be the compressor. Quoted me $1500-$2000 for a new compressor. Wondering if I should try to repair the current compressor, or do some other troubleshooting, or just bite the bullet.

I love the car, and it's only got 42K miles (2016 Black 40e), but already put new batteries ($900) and air springs ($1000) in the last 18 months, and I assume it will only get more costly from here.

[5tony]

Mine sagged after replacing both rear springs. Fixed by clipping 1/4 inch of the end of the air tubes where they connect to the airbags.

[Chilled]

Originally Posted by nuggetman

I discharged & refilled the bellows via ISTA without issue but now the ride height is low and the compressor never kicks to top the bags up. I tried the ride height calibration and the sensors are showing 701mm/704mm height in the rear left/right sides which are the same values I get when measuring manually with tape.

Hey, where in ISTA did you go to get the measurement? The calibration videos I've seen all say to manually measure with tape and input that. I couldn't find any option just to do a simple current value read out.

[Chilled]

For Anyone that comes looking after, yes you can. See post.
https://f15.bimmerpost.com/forums/sh...0#post28953490