Hello All,

New to this and not too knowledgeable about cars so bear with me and grateful to anyone who spends the time passing advice.

I own a 2011 xc90, good condition, which I bought second hand about 6 months ago. Unfortunately I started noticing an issue with the front right break (driver's side) shortly after buying it - whenever the car was loaded or I was aggressive on the breaks or I was going down a steep hill the brake, when used, would start to emit a thudder (no other way to explain it). No vibrations just a noise. It would continue for a little while after removing my foot from the brake pedal, albeit at a lower volume, and would temporarily cease if I applied a marginal amount of pressure on the brake pedal again.
Last week I took the car for its annual service and asked the guys to have a look at the issue. It turned out there was a significant amount of corrosion on all wheels and my rear brake pads were shot. They therefore replaced all the rotors and the rear pads and believed it was the reason for the noise.
Although the thudder seemed to have gone it seems to have been replaced with a noticeable whining noise (again, no other way to describe it!). One oticeable change is that the noise only seems to happen when I am driving and not using the brake but there still seems to be a correlation between brake usage / heat and noise.

My guess, and this is from somebody who has 5 days of post reading knowledge to go on, is that one of the pistons is slow to release, possibly caused by the heat of the brake, resulting in a friction between the pad and new rotor.

Has anybody experienced this or have any suggestions? I am going to take it back to the garage for them to have a look but would prefer not to be paying to change everything until the problem is resolved.

Thanks again.