I have a rattle behind the dash on my S1, on the drivers side. It sounds as if the speedo had a bad bearing, but the noise is there whenever the engine is running and when I tap the gas pedal lightly the noise goes away. At idle it is not really there, but just off idle it becomes audible. It doesn’t change in relation to engine or road speed, and pushing the brake pedal has no effect. Once I open the door the exhaust is too loud to follow the noise to the source.
Since no tubes, wires or cables make the noise, could it be a bad valve inside the brake booster that isn’t sealing right and starts to chatter or vibrate when the vacuum is high? I don’t want to remove the vacuum hose for now since it’s not so easy to access and I don’t want to break the inlet on the booster. Anyone with a similar experience or who can point me to what causes the buzz, would be greatly appreciated. @peder , were you able to fix the Mk9 rattle?