528iT wagon's jiggles, rear suspension ? variation on the theme

[jiggapoo]

Non-sport, '99 528iT with 195k. Lots of miles, I know, but suspension is original. One thing I haven't noticed in a while is the 'leveling' of the rear suspension. I.e., if you put something heavy in the rear it doesn't pump-it-up. And when you take it out it doesn't un-pump... The ride has gotten harsh, to say the least. It is as tight as tight can be. When riding at night the rear of the car bounces and responds to each little hairline crack in the road and causes the headlights to do a dance. Visually it does not look like the rear suspension is over-inflated or underinflated; ride height appears normal.

Diagnosis? I know there is a load leveling sensor on the axle but didn't identify it yet. No rust or grime in the undercarriage. No obvious leakage of the shocks or rear suspension hydraulics. Do the shocks ever fail in the "inflated" state?

[oekundar]

I recommend you check the Touring thread, but it sounds as if its time to swap out the bags and possibly sensors as age might have caught up to them.

[edjack]

Subframe bushings are causing the harsh ride. They often wear out long before 100k.

Self-leveling suspension needs some troubleshooting, unless someone has had this same problem, and knows what's wrong.

[jase007]

Tourings really beat up the rear subframe bushings, especialyl the two closest to the front of the car. Lots of touring owners have replaced theirs and the improvement in ride quality is tremendous.

Search the forums in the DIY section to see the procedure. You can save lots of $$$ if you DIY this. You only need 3-4 hours to do the work.

Cheers.

[jiggapoo]

Okay, subframe bushings are probably needed. But I can't imagine that causing the suspension to be not-adjusting. Is my non-adjusting problem a common sensor issue?

[jase007]

Look underneath on the rear control arms and make sure that the ride height level sensor is 1. attached 2. intact 3. electrical connection is where it is supposed to be.

The EHC is pretty good about throwing code and the control module has a self-test, constant monitor, self-adjust mode.

To make sure it is still working, load up the back or climb in there. Do it with the car running, rear hatch open ... you should hear the air pump running in the spare tire well.

Mine runs when I put it in reverse (supposed to), back out of my driveway everyday onto a downhill road (adjusting ride height b/c car rocks significantly r to L to R when crossing into road), load up the rear, add kids (from when I last drive it), etc..

I have an EHC pdf document that describes the design and operation modes (startup, rest, moving, transport). I believe it is the same as the one in the TIS.

[GTMule]

Are you sure it had SLS? You say it's a non-sport....I thought non-sport's were all/mostly non-SLS.... Mine certainly doesn't have SLS...



Non-sport, '99 528iT with 195k. Lots of miles, I know, but suspension is original. One thing I haven't noticed in a while is the 'leveling' of the rear suspension. I.e., if you put something heavy in the rear it doesn't pump-it-up. And when you take it out it doesn't un-pump... The ride has gotten harsh, to say the least. It is as tight as tight can be. When riding at night the rear of the car bounces and responds to each little hairline crack in the road and causes the headlights to do a dance. Visually it does not look like the rear suspension is over-inflated or underinflated; ride height appears normal.

Diagnosis? I know there is a load leveling sensor on the axle but didn't identify it yet. No rust or grime in the undercarriage. No obvious leakage of the shocks or rear suspension hydraulics. Do the shocks ever fail in the "inflated" state?