sakimano

As described, the car (a 2001 S430 4matic) has started to slowly rise, when running, but stopped at a red light or stop sign or in traffic.

No previous Airmatic problems up to this point.

Anyone had this happen? Probably won't DIY fix it, but just wondering what the likely repair solution/bill might be.

Thanks!

tusabes

My car does this too., the car lowers at freeway speeds and rises when you come to a stop, do you notice this coming off a freeway offramp to a stop sign?

if so, that is normal.

If it is happening at slow speeds in town, you may have a leak, spray some soapy water on the strut tops inside the engine compartment and check for bubbles

Skylaw

Tusabes, do you keep your car in the "raised" position? That's the only time what you describe should occur.

Driving the car raised decreases its stability; it is supposed to be used if you're encountering particularly rough roads, or using chains.

Arnee

Actually, he is correct.

There is hysteresis with the raising/lowering.

Starting from the normal height setting:
1) From 0 km/h, the car lowers automatically at v >110 km/h to -5mm
2) From 110km/h, the car raises automatically at v <60 km/h back to normal height

Starting from "Raised Level" (+30mm) setting:
1) Raised level is canceled after 5 mins if v > 80 km/h
2) Raised level is canceled immediately if v > 120 km/h and lowered automatically to -5mm

One *may* notice the 5mm raising from the normal height setting if the car decelerates from >110 km/h to <60 km/h immediately. Additionally, the valves are not lowered at the same time; the rears may release pressure first THEN the fronts, hence the delta of 5mm *may* seem more.

tusabes

thanks for laying out the details arnee

Skylaw

Arnee,

What type of hysteresis is creating the lowering? What part of the system does it occur in? Are the ride height sensors set to create this?

Arnee

The airmatic module itself creates the hysteresis on lowering/raising at various speeds.

It's programmed that way. The airmatic module gets input from the steering wheel sensor, speed sensor, etc.

The height sensors are just there to provide feedback to the module.

Per the WIS, this is how it's done. I wish I could post all the pages from the WIS. There's a lot of info from it on the airmatic function.

Skylaw

So then it is specific programming of the module that causes the raising and lowering - thanks. I was aware of the second half of your initial post - lowering the car if it was raised, above a certain speed for a certain time; and then raising it again at lower speeds. The amount of rise with the dash switch is 3/4 inch.

I learned something with the other information you provided. Very interesting. At 5 mm rise/lowering, that's just under 1/4 inch, and it could be visible to the driver.