[Oosen1]

Hi, Can anyone help? My rear suspension keeps sinking on one side. This happens over night and comes back up once you start the car.

[sunnyman12]

wierd....

[coolraoul]

Does it have some sort of pneumatic rear suspension? It could leak air or pressure...Once started, the car senses it and correct it... But BMW does not offer this kind of suspensions on the 5er from what I know.

Does it have the system that makes the rear suspensions harder when you put weight in it? The weight-compensating rear suspension? I know MB usually put it on its station-wagons, but on BMW it's more rare.

On a 1997 BMW it should be an electronic system, so only working when the car has started. I think it could be that, because your car goes up again when it's started, if I understood well?

Maybe it's the problem that the "standard" suspension setting (eg. with the ignition off) is wrong on one side (leaking oil on the suspension arm maybe), so it sinks a bit because it's softer on one side, and when you start it the sensor makes the car even because it senses the problem.

However then, you should have a warning in the dash I think...but not necessarily if the problem is mechanical, on the suspension arm and not on the weight-sensor.

If it has no this system I don't see, a car that sinks is not that uncommon (broken suspension arm, oil-leaking suspension, pressure-leaking pneumatic arm) but a car with metal suspension and sinks when off, but goes up again when started, ???

You should try to see if the suspension arm is not oily, or much more dirty than the others. You also could do the famous test: open the boot, and push the car (hard!) vertically from one side, and then the other side, to see if one side is softer or has more rebound. It's not very reliable but could show a problem if it's very obvious.

It could be the sinking side that is too soft because of a tired suspension, or the other that is too strong because the suspension has no power and does not stop the move of the car. The it will have a lot of rebound, and this side will sit higher.

There a possibilities to test the suspensions of a car, to see if one (or more) are not working good, or if there are differences in one. Not very reliable test, and only shows a dead suspension, but an independant mechanic could do it for less than BMW.

The strange thing is that everything goes back to normal when the car is ignited, which makes me think to this weight-compensation system used on station-wagons.

[Oosen1]

Hi Thank you,
It is I believe the electronic suspension system. it sounds like it could be some sort of sensor issue as it is fine once you have started the vehicle. I may have to investigate further. Thnks again

[coolraoul]

I think it's not a sensor issue, because if it was the problem would appear when the car is started (so the sensor is activated).

I think it's a mechanical problem on the suspension arm, that the sensor detects and corrects when the car is started.

I think what you have is a mechanical, conventional suspension, with a weight-sensor that can change the softness of the suspension in relation to the weight in the car. It's not a pneumatic suspension from what I know. So for me it's probably an oil-leaking damper, or something like that, but I'm not an engineer.

You should look at your suspension damper to see if one is not oily or very very dirty compared to the others. It's showing a dead damper.