4.8is; are front and rear air bags/struts linked together?

[Turbo_Bimmer]

I have my front right deflating overnight, and my rear right is also a bit lower, but not as much as the front. They inflate on door opening and I don't see any error message on the display.

I don't think that both air bags went bad on the same day, so, are the front and rear linked in anyways together in the air circuit.?
If the front leaks air, is it going to affect the height of the rear one, even if it is good?

I didn't have time to check with soapy water yet since it happened for the first time on Monday. I will check this weekend the 4 airbags.

In the meantime, I have downloaded the BMW training pdf on the air system, but it is only general information, no pneumatic drawings.

[Icer006]

Every 6 hrs, the EHC will compensate. If the fronts deflate, the EHC will compensate the rears to have [close to] similar heights.

This is not good for the rear bags and the pump, as we know, since the pump would have to reapply pressure to inflate both front, rear, and the tank.

[Turbo_Bimmer]

Originally Posted by Icer006

Every 6 hrs, the EHC will compensate. If the fronts deflate, the EHC will compensate the rears to have [close to] similar heights.

This is not good for the rear bags and the pump, as we know, since the pump would have to reapply pressure to inflate both front, rear, and the tank.

Icer, do you mean that the system will use some air in the tank to try to inflate the front, and deflate intentionnally the rear to try to match?

I never heard my pump working. Many people say they ear the pump. I guess I will have to remove the rear floor and junk that is stuffed under it. I have no idea on many time the compressor starts.

[Icer006]

Originally Posted by Turbo_Bimmer

Icer, do you mean that the system will use some air in the tank to try to inflate the front, and deflate intentionnally the rear to try to match?

I never heard my pump working. Many people say they ear the pump. I guess I will have to remove the rear floor and junk that is stuffed under it. I have no idea on many time the compressor starts.

From what I understand, it will deflate your rear bags but not inflate the fronts, since during sleep/rest mode, the pump is not on.

During wake-up (door open or ignition), the pump will increase pressure on both front, rear, and tank.

I've had this happen on my truck when the front passenger had a leak. I thought for sure the rear was toast but nope.

Upon ignition, you should be able to hear the pump working. It's a different sound. For me, it was very noticeable after I replaced the faulty pump with a brand new one.

[ECS Tuning]

The system should be letting air out of the system to try to level the X5, not putting air in the bags. In the past I've seen X5s completely aired out over night as the system tries to level the truck while it is parked on very un even surfaces.

[Turbo_Bimmer]

Thanks Icer and ECS. At least now I can hope that only my front is defective, not the rear also.

I didn't know that the suspension control was waking up every 6 hours to monitor and correct the stance of the X5. Nice little beast ... when they work

I will take a look this weekend, stay tuned.

[Icer006]

If it's any consolation, the rear airbags are easy to replace and relatively cheaper than the fronts. The pump is easy to replace also.

Here's the specific text that I have:

Control Modes
Sleep mode
If the vehicle is parked, it enters Sleep mode after 16 minutes. No further control operations are executed. A "watch dog" wakes up the control unit for a few minutes every 6 hours (wakeup mode) in order to compensate for possible inclination of the vehicle. (Vehicle height may only be corrected once as air supply unit only operates with engine running.)

Wake-up
In wake-up mode, the control unit is woken up for a set period of time in order to compensate for possible inclination of the vehicle. Inclination of the vehicle can be caused by large temperature differences or by minor leaks. Adjustments to the front and rear axles ensure that the vehicle is visually level. To minimize power consumption, the vehicle is lowered only. The nominal level of the lowest wheel serves as the nominal level for all other wheels. The lowest nominal level to which the vehicle is lowered is the Access level (-35 mm).

Exception: if the vehicle is parked at Access level, the vehicle is lowered to max. -50 mm
in wake-up mode. If the vehicle is parked for a prolonged period of time and there is a leak in the system, further loss of pressure does not produce a change of ride level since the weight of the body is born by the auxiliary suspension and the residual tire pressure.

Advance /Overrun
When the vehicle is woken out of sleep mode by the load-cutout signal (VA), it normally
enters advance / overrun mode. Since the engine is not (no longer) running in this mode,
however, there are restrictions on the control operations that can be performed in order to conserve the battery. Ride level compensation is restricted to tolerance ranges of 20 mm and 25 mm in the up and down directions respectively. This serves to reduce the frequency of control operations.

[Turbo_Bimmer]

Interresting information Icer.
Thank you.

[PUREVIL]

There is a common link. If you remove the black under-body trim that runs below the passenger door between the front and rear wheel wells you will find the accumulator (tank). Attached to the front end of it is a "valve" that supplies air to all four corners.

You'll need an 8mm, 10mm, and something to pry the plastic body fasteners apart to get in there. It's super easy, just be sure you make note of the two screws way up front. They are also holding the bottom of the front inner wheel well so they can be overlooked.

My advice on the topic which you can take or leave:
Opening up the bottom side should only be done to soap/water test for leaks. Do not disconnect or loosen anything. (I did and actually caused more problems).
You are likely to find one leaking airbag causing all of your problems but finding the leak can prove to be difficult.
Don't overlook the obvious - open the hood, remove the round, black covers on the strut towers and hit them with soapy water. See what happens. If no leak, spray down the bags themselves and also the fittings going into the bags. If still no leak, move to the back and try the rear bags. If you still haven't seen a bubble, open the trunk and flip the compressor out so you can squirt the fittings there. Lastly, remove the bottom cover and check under the passenger door.
By now, you've found your leak - if not, start over because it has to be there somewhere.

[Turbo_Bimmer]

Thanks for the suggestions Purevil.
I will start with the airbags, and hopefully I won't have to search deeper.