noisey brakes when powering up!!

[john brooks]

my first time on the forum, my first merc...E320 cdi...my first funny noise.
when car has been stood overnight or for a few hours there is a strange 'whirring' sound from under the bonnet when doors are unlocked. It's a similar sound to the wing mirrors opening. it also seems to do this at random times when the breaks have been applied(traffic lights etc)
I've just had a 'B'service and the service manager tells me it's normal, just the breaks powering themselvesup. surely a car of this quality shouldn't have noises like this. Can anybody put my mind at rest?

 

[alan782]

Mine makes the same noises, i dont think its anything to worry about but i am sure Television will be here any second to throw a proper explanation.

 

[alan782]

Oh and welcome. Sorry should have put that in the firt one.

 

[jberks]

Its the SBC pump repriming. Your braking system is fully electronic and is powered by an electric pump rather than the old fashioned engine driven vacuum system.
Lots of people didn't like it so they've done away with it in the new models but yes it's perfectly normal on yours and mine, they all do it and you do get used to it.

Console yourself with the fact that you have one of the most advanced braking systems in any production car, ever, and thats what you can hear. As it's electronic, it can fire up at any time and will self test from time to time. Common times are when you unlock or open a door (self-tests as it's expecting to be going somewhere). It even dries out the brake pads automatically in the rain. Just don't attempt to change the brake pads without disabling it or it could have your fingers off!

 

[television]

As Jberks above,,it is the SBC brakes.

During the last 2 re calls it has been set to run longer when the ignition is turned on or a door opened, as the car thinks that it id going to be driven