G12 750i Ride height error

[Recon3D]

Hello guys, I'm having some issues with my G12 with the self leveling suspension. I noticed that my corners of the car will randomly sag sometimes overnight after parked and I'm not sure why. When I drive the car in comfort or sport, I don't get any chassis malfunction codes and the car stays level.

If I try to put the car in the highest setting using the button to raise it, the rear starts inflating, however, the front doesn't start inflating and I get a chassis error code (482974 - VDP: Vehicle level - not adjustable). I also hear the compressor louder than before. To me it sounds like a compressor/valve block issue?

Steps I've done to troubleshoot issue:
*Deleted the chassis fault and registered the correct ride height via ISTA
*Installed a new AUX battery and registered it.

[Raimo5]

The fact that suspension is sagging tells me that there is a leak in the system. This leak could be in air struts, air lines or compressor and valve assembly.

Why you are hearing compressor louder than before is because it is working hard - too hard. Normally, you should never hear compressor run, because it rarely ever runs, and if it does, it's pretty silent. All the needed air is stored in pressure accumulation tanks.

When you develop a leak somewhere in the system then compressor has to run a lot more than it was ever designed to. This will destroy the compressor in very short time. Usually it gets audible before it dies, so I bet yours is on its last legs.

Good news is that as I understand from your other post regarding HSR battery, you are still under factory warranty. This should cover all components of air ride. There is also extended milage goodwill warranty for air struts.

[JustJosh]

What year is it? If its a 17' plus, there is a service bulletin that might still cover your suspension. I have a 16' and was able to get two of the struts replaced under warranty. That ended in October for me.

For me that wasn't all I needed. I also replaced the compressor and two air lines through a private shop since the warranty only covers the struts.

[Recon3D]

Originally Posted by Raimo5

The fact that suspension is sagging tells me that there is a leak in the system. This leak could be in air struts, air lines or compressor and valve assembly.

Why you are hearing compressor louder than before is because it is working hard - too hard. Normally, you should never hear compressor run, because it rarely ever runs, and if it does, it's pretty silent. All the needed air is stored in pressure accumulation tanks.

When you develop a leak somewhere in the system then compressor has to run a lot more than it was ever designed to. This will destroy the compressor in very short time. Usually it gets audible before it dies, so I bet yours is on its last legs.

Good news is that as I understand from your other post regarding HSR battery, you are still under factory warranty. This should cover all components of air ride. There is also extended milage goodwill warranty for air struts.

It's really strange that all corners leak out of nowhere. It was fine one day, then every other day a different corner of the car would be sagging. Sometimes a whole side, sometimes only one corner. I have also noticed that if the strut fully extends due to a slope, it will make an audible whoosh (like a ballon deflating) and the corner/strut that was fully extended will deflate (eventually re-inflating).

I found the Service Bulletin (SIB 01 05 22) on the extended warranty for the air struts (My car is a 2016 with 67k miles). If you have any more info on this I would greatly appreciate it!!

Edit: Should I start troubleshooting this issue with an air compressor replacement first or my taking it to the dealer in hopes that they replace the faulty struts?

[Recon3D]

Originally Posted by JustJosh

What year is it? If its a 17' plus, there is a service bulletin that might still cover your suspension. I have a 16' and was able to get two of the struts replaced under warranty. That ended in October for me.

For me that wasn't all I needed. I also replaced the compressor and two air lines through a private shop since the warranty only covers the struts.

It's a 2016 750i xdrive, although I see the Service Bulletin states my model should be covered 8yr/80k miles. I have a feeling that I'll probably need a compressor and possible lines replacement as well.

Will the dealer test the struts for leaks or how exactly will they determine if the struts need replacing if my car randomly sags?

[Raimo5]

Take it to a dealer and let them take a look at it. They must have some specific procedures to determine faults in air ride system. They mostly get the diagnosis and repairs right, as far as I have gathered.

Do not replace the compressor before you haven't figured out what exactly is the issue. Doing that might very quickly kill the new compressor, as it has to run well past its design specs to accommodate for a leak elsewhere in system. As you can hear air noises coming from strut areas, then good possibility is that there is a leak in one or more. If that is the case, then I think BMW will have you covered. If you have to go out on a pocket for a new compressor after that, then so be it. At least you have new struts on the house and the compressor you will have to buy wont blow up after couple hundred miles.

Be aware that I have also seen air ride do funny things when VDP module is defective. At any rate, it needs to be properly diagnosed before anything is done.

[dc5525]

Originally Posted by Recon3D

It's really strange that all corners leak out of nowhere. It was fine one day, then every other day a different corner of the car would be sagging. Sometimes a whole side, sometimes only one corner. I have also noticed that if the strut fully extends due to a slope, it will make an audible whoosh (like a ballon deflating) and the corner/strut that was fully extended will deflate (eventually re-inflating).

I found the Service Bulletin (SIB 01 05 22) on the extended warranty for the air struts (My car is a 2016 with 67k miles). If you have any more info on this I would greatly appreciate it!!

Edit: Should I start troubleshooting this issue with an air compressor replacement first or my taking it to the dealer in hopes that they replace the faulty struts?

Glad you found the bulletin, get it to the dealer service shop ASAP. You are covered. Warranty will not cover a blown compressor...and that could possibly happen if you continue to drive the car in this condition.

[Recon3D]

Originally Posted by Raimo5

Take it to a dealer and let them take a look at it. They must have some specific procedures to determine faults in air ride system. They mostly get the diagnosis and repairs right, as far as I have gathered.

Do not replace the compressor before you haven't figured out what exactly is the issue. Doing that might very quickly kill the new compressor, as it has to run well past its design specs to accommodate for a leak elsewhere in system. As you can hear air noises coming from strut areas, then good possibility is that there is a leak in one or more. If that is the case, then I think BMW will have you covered. If you have to go out on a pocket for a new compressor after that, then so be it. At least you have new struts on the house and the compressor you will have to buy wont blow up after couple hundred miles.

Be aware that I have also seen air ride do funny things when VDP module is defective. At any rate, it needs to be properly diagnosed before anything is done.

Just to report back on this issue. Took it to the dealer and after they performed their diagnosis, they discovered that the front left is leaking. They will be replacing both front left/right air struts under the extended warranty.

Will update further if issue is fully fixed after I get the car back. The part that doesn't quite make sense is why one of the days when I went outside, the entire left side of the car was sagging (including the rear left).

[Raimo5]

Originally Posted by Recon3D

The part that doesn't quite make sense is why one of the days when I went outside, the entire left side of the car was sagging (including the rear left).

The way that air is moved around in accumulation tanks and different lines during balancing in defective condition can lead to all kinds of upset conditions. It is very common with leaky air struts, which is why I also didn't focus on it during my initial query.

Oh and glad to hear that BMW has you covered for the repairs.

[Recon3D]

After getting the car back and driving it for a bit, it does indeed seem that the issue was fixed due to the air spring replacement.

Something interesting that I noticed when I looked over the paperwork is that the part numbers for the front left/right air springs are not what I expected. I tried to cross reference the parts, however, I don't see them listed on any bmw parts website. Searching Realoem also doesn't result in anything. The paperwork lists the following parts that were replaced:

Air Spring Front left: #37105A4A615
Air Spring Front Right: #37105A4A666

While searching online for these parts, these parts seem to be significantly cheaper than the entire strut replacement that I saw on various websites. So I could only wonder if this was a repair/service kit for the airbag portion?

Nonetheless the car drives as it should

[Raimo5]

Yes, these should be entire air spring portion of the strut. They now make repair kits like that. What they do is take damper out of the old air strut and install it into new one, as hydraulic dampers themselves are rarely the issue on lower milage cars, and those EDC dampers aint cheap.

Thanks for reporting back with the codes. These might come very handy for someone who has to do this job out of the pocket.

[HamsaAden]

I’m also having the same issue but worser, my front passenger side is sagging when the car is level but the suspension has become unlevel, this happens 3 times a week and it usually goes away after a bit of driving but it hasn’t gone away today. Here are the images

[M_Bimmer]

Originally Posted by HamsaAden

I’m also having the same issue but worser, my front passenger side is sagging when the car is level but the suspension has become unlevel, this happens 3 times a week and it usually goes away after a bit of driving but it hasn’t gone away today. Here are the images

I've seen this, but a lot less exaggerated than what has happened on your vehicle.

1. Has your car had any work done where the car was raised off the ground? If. so, and the self-leveling was NOT turned off before the tires left the ground, this could explain your situation, and you'll need to rerun the self-leveling procedure in ISTA.
   
   
2. Another issue could be that your leveling sensor arms are reversed on one or more wheel, which can happen if the car has been raised off the ground, and the suspension fully extended sensor's arm, then when it was lowered, the arm went to the wrong side of the sensor. This can happen much easier if the sensor bracket is bent, or if the arm is bent. This is really easy to check.
   
   
3. Another issue is that you have water in your air lines. and with the suspension doing multiple self-leveling activities after you shut your engine off, and the water freezes, the car adds air, but it blocked or your air block is frozen, this will result in a lop-sided leveling event.

Below is an excerpt from TIS:

Notes on vehicle tilt (2-axle air suspension)

System-related causes (no faults)

• Control tolerance when "Ignition on" and "Engine off: ± 20 mm to nominal ride-level height (attention: at the front axle, the control variable is the mean value of the right and left ride height).
• Control tolerance when "Ignition on" and "Engine on: +/- 9 mm relative to nominal ride-level height (attention: at the front axle, the mean value of the right and left ride height applies).
• When the doors are open, an automatic level correction does not take place (an active control procedure is aborted). Level changes that are requested with buttons will not be carried out when the doors are open (level changes in progress will be interrupted).
• If the vehicle was located on a vehicle hoist and the vehicle level no longer self-corrects, move the vehicle for t > 5 s with v > 6 km/h
• Vehicle inclination can only be checked on level and horizontal ground. For technical reasons, it is not possible to adjust all wheel stations to the nominal ride-level height on uneven surfaces. For example, if the one wheel of the vehicle is on the kerb, the resulting inclination is not corrected.
• Active wheel relief mode: To relieve a depressurised tyre, the vehicle is inclined using the air suspension. This mode is linked to the tyre pressure control and is not closed until the tyre pressure control no longer detects a tyre pressure loss.

Temperature influence
The air in the spring struts is warmed by the engine heat and damper work and expands. This raises the vehicle. During the journey, ride height changes due to temperature changes in the air suspension struts are corrected. When the vehicle is stationary and switched off, these temperature effects may lead to ride height changes and inclinations that are not corrected. When the engine is hot, an after-heating effect occurs after the vehicle is stopped that causes the vehicle to first be raised slightly within the first hour and be lowered again during the cooling-down period. In extreme cases, the temperature effect on the front axle may cause the vehicle to be lowered up to 50 mm. After the vehicle is parked, the self-levelling suspension performs up to six control procedures within the first 48 h during which, depending on the system availability, an attempt is made to reduce possible inclinations by raising or lowering the vehicle to a horizontal level. The self-levelling suspension may hereby lower the vehicle to up to 40 mm below the normal level. For technical reasons, inclinations in vehicles that have been parked for lengthy periods cannot be avoided in air suspension systems. Workshops are not able to check the control functions in parked vehicles due to the system complexity.

Checking the ride height adjustment

• Adjust the vehicle to the normal level
• Read out the front left, front right, rear left and rear right ride heights via the diagnosis system
• Measure the ride height of the vehicle
• Compare the measured ride height with the nominal value
• Ride height = measured value – nominal value
• In the event of deviations > of 3 mm from the setpoint value, adjust the ride height with the diagnosis system

Possible causes of mechanical faults

• Sensor linkage reversed (sensor arms must always face outward, rear axle: connector faces inward). Refer to Repair instructions
• Sensor bracket twisted (holder in centering bore? Holder must be flush with rear axle support)
• Sensor linkage torn or bent
• Leakage (test, see below)

Possible causes of electrical faults

• Water in the connector (corroded contacts) -> exchange the sensor and connector. Sensor signal is corrupted by voltage drop. Gradual process
• Short circuit (detected by control unit and Check Control message displayed)

Check for leaks
Larger leaks can be found using the following procedure. The determination for small leaks is significantly more extensive and lengthy to exclude effects from temperature changes and axle strain. According to the specifications, the leak may reach up to 2 mm per day (constant temperature, vehicle is parked on skid-proof plates -> no axle strain).

• Park the vehicle approximately 10 - 12 H in a room with largely constant temperature (+/- 3 °C) and adjust it to the normal level. Do not set the parking brake!
• If the vehicle ride-level height deviates from the nominal ride-level height by more than +/- 10 mm, adjust the vehicle to the normal level again (ignition on, door open –> all doors closed, adjust level, ignition off; let the engine run in emergencies only and only for a very brief time. Do not get into the vehicle).
• Place the EHC control unit into production mode via the diagnosis and information system (deactivated level controller)
• Measure and note down the ride heights
• Leave the vehicle parked for another 10 - 12 h (constant temperature, do not move the vehicle, do not get in or out or make any other load changes)
• Measure and note down the ride heights
• If the ride heights are lower than the initial measurement by more than 10 mm at one or more wheel stations, it can be concluded that there is a leak. Leaks may occur at the air lines, the pneumatic connecting elements and the spring strut.
• After completion of the leakage test, deactivate production mode again.

[HamsaAden]

Thanks for the reply, my car has not been on a lift at all. This suspension issue started one rainy day and the warning that popped on the screen was “Chassis Function Limited” but the uneven suspension problem seems to only happen when it snows and when it’s very cold outside.