breaks whistling

What's a break?? Do you mean brakes? Maybe the brakes are happy!

Any how if you mean brakes, a build up of rust can occur on the disk. Due to the design of a disk brake and with the close tolerances of the brake pad to disk a scraping noise can occur - similar to a whistle until the rust clears. This generally only happens after the car has been sitting for a few days or longer in a moist environment. What it could also be is that the calipers are sticking. Have you had a brake job recently? How old is the car and how may miles do you have on it?

Yes,

Mine is the same case. But I take my Ford Focus(49k miles) out everyday to work. They squeak for first 2 or 3 times and then disappear. If it is raining, then i have noticed, it does squeak more often.

What should I do?

Rahul

I have the same problem sounds like it is coming from the left rear brake drumb.

I had a focus come in and it went away as soon as i took the drum of that side and put it on. so im guessing it might to have something to do with the Brake dust. Maybe getting stuck in the springs or something like that.

it was very werid. Also i've notice alot of Wheel Cylenders going on the focuses, but then again people that come to my shop drive them to the ground 100k with out anything done to them and wonder why i give them a bill for a large amount!! :)