dec535i

So, here is a real tough problem that BMW is trying to tell me is not a problem. The symptoms started a year ago. When I come to stop I can hear a clicking/actuation noise coming from the rear passenger area of the car. At first I thought it was the gas cap actuator. I then realized it was the dynamic drive system. I can remove the fuse and the noise disappears. I took it in under warranty and BMW has replaced everything from the valve block, rear sway bar, hydraulic lines, etc...over the past year. The noise has persisted and they used the chassis ears to figure out it was the hydraulic lines going to the rear sway bar. The interesting thing though is that after they have the car and supposedly bleed the system, the noise is gone for about a day and then returns. They don't believe me though! They are now claiming that the car is 'operating as designed'. This is total BS. I get dynamic drive faults every couple months and a very annoying noise every time I come to a complete stop. They insulated the hydraulic lines in an attempt to reduce the noise, but it didn't help much. I've read a few posts on the Internet where other people have had this issue, but haven't found any solutions other than possibly the steering pump. I have a meeting with the director of service at my dealer next week to 'resolve this issue' but I want information to go in with. Have any of you had this issue? I read that there was a PUMA case in 2005 for a 530i that had the same issue. Are there any BMW mechanics that can do a quick search on the PUMA database related and see if there have been any resolutions to a similar issue?

TU2TLE

you catch many more bees with honey then with s*** . Don't go in a meeting with the director with a mentality that you want to open up a puma case and threaten them that what they are doing is incorrect. Hear them out see what they have to offer, then let them hear you out. be amicable, respectful, and professional. the less bad they have to say about you to BWW corporate the better. And if they get out of line and they disrespect you, treat you in a manner you should not be treated, that will completely fall in your favor. Good luck.

BimmerFan52

The front sway bar torsional valve has two lines that allow filtered air to enter the valve to prevent noise from cavitation of air bubbles (probably the noise you are complaining of).

I haven't been under my rear end in a while but I would guess the rear sway bar torsional valve has the same air relief lines.

The dealer needs to check that these lines are not blocked or obstructed.

turboawd

there may be something loose back there?? sway bar links?
the only thing regarding the dynamic drive going to the rear, are two hydraulic lines that run under the passenger side of the car, and the rear antisway bar.

here is a test example. has the dealer performed this test for you to see? this would show you if the noise you're hearing is dynamic drive related.

BimmerFan52

I checked the rear active stabilizer bar on my 545i and there are no pressure relief air lines.

I researched their omission, and BMW claims they are not needed in the rear : "Since no noises can be heard at the rear axle, the pressure relief valves have been omitted from the rear oscillating motor."

You are obviously hearing it so it is possible that the torsional valve (BMW calls it the oscillating motor) is defective.

turboawd

you could slap a gopro camera under the car by the sway bar and go for a ride. then watch video back to see if noise comes from sway bar??

dec535i

Thanks for advice and thoughts. Yeah, they thought sway bar/Osillating motor was bad and replaced that with valve block. No luck. That was on 2nd visit. On subsequent visits try replaces the lines. I also saw that there are no valves in the rear like the front. I'm out of town today but I want to check and see if I can see micro bubbles (ie air) in the reservoir after driving. I do believe what I'm hearing is cavitation. BMW has confirmed the noise is from the hydraulic lines. This may explain why the noise seems Togo away after they open the system and bleed it for a few hours and then slowly comes back.

I convinced them to compare my car to another one with similar options and see if the noise is present in the other car. Not sure what will happen when they realize its not, but ill take it step by step. Still looking for any good ideas about what may be bad here.

BimmerFan52

Actually in my first post I did a poor job of explaining the process.
The cavitation and noise is caused by vacuum pockets in the fluid. The air lines allow air to enter the fluid, reducing the noise. The air bubbles formed then tend to absorb into the fluid or are released in the reservoir, which has an air relief hole in the filler cap.

I don't know if the air bubbles would be visible in the reservoir after an aggressive drive.

eivissa

So did you solve this clicking issue? I am facing the exact same clicking noise from the rear right direction at slow speeds after the engine warmed up. Its indused by small steering corrections around the middle axis and braking to a complete stop when the rear axle is back on its way down.