Brakes Whistling until brakes pedal depressed C270CDi Auto

[stumcfc]

Any Ideas ?
After lifting my foot off the brake pedal - say after sitting at lights - there is a continuos high pitched whistling ( seemingly insided the car -or poss through vents ? )
This whistling immediately stops when the brakes are applied .
then when brakes are released the whistling starts again , and so on , so on.
The whistle carries on for about 30-45 seconds if brakes are not needed then dies outto silence -- but once again returns after applying then releasing brakes ?

 

[machasm]

It sounds like they are dragging just a touch. Also have you checked that the anti-squeal shims are in place? (assuming you have some).
You should also be able to apply some anti-squeal compound between the back of the brake pads and the brake piston. This should help.
mac.

 

[david55amg]

I had a squealing brake until I replaced the crappy brake pads which occupied the calipers (the previous owners, not me!!) and replaced them with OEM pads from gsf. all is perfect now . I mean, WHY put cheap pads in a 320clk when the price difference can only be a few quid!! the braking performance now is right up to scratch!!!! Sorry, i've had a few, I'll get off my soapbox now

 

[pipehose]

Any Ideas ?
After lifting my foot off the brake pedal - say after sitting at lights - there is a continuos high pitched whistling ( seemingly insided the car -or poss through vents ? )
This whistling immediately stops when the brakes are applied .
then when brakes are released the whistling starts again , and so on , so on.
The whistle carries on for about 30-45 seconds if brakes are not needed then dies outto silence -- but once again returns after applying then releasing brakes ?

i think he means when he sitting stationery ie at traffic lights
this is happening

 

[SSBB]

Its possible that the cooling fan (blower motor) for the cars interior is whining due to normal wear and tear or dust buildup, when you apply the brakes you cause a current drain on the battery and a resulting decrease (slight / temporary) in available current on other items using power, this is enough to slow the fan down a tiny bit and stop the noise until it picks up speed again and you hear the noise till the fan settles down. I had a similar fan problem that I solved by switching it between maximum and minimum several times, the only real solution is a strip/clean/inspect/or replace.
Just a suggestion, as when you stop the car there's nothing brake related to whine......if your moving though...see the above posts.

 

[Dieselman]

If this is when stationary then I would go for ti being the servo vacuum valve whistling. When the brakes are applied the valve closes so vacuum is built up in the servo, when released the valve opens so the vacuum is bled away from the diapragm.