Kind of annoyed at the van finally thought I had everything except an oil leak fixed and then a new problem is here.
Yesterday driving at city speed and braking all of a sudden a low pitched "shroo" sound appeared from the right side disc brake/wheel well. I've done two test drives since I heard it the first time. It kind of happens randomly it seems, when pressing the brake pedal it brakes completely normally without any feel of uneven pull to one side or the other but the "shroo" sound appears and continues after releasing the pedal, and sometimes goes away when braking the next time or just pushing the brake down lightly a few times.
Drove it some 40km today, both city and highway, no problem but one or two times when braking more intensively the sound appeared again for briefer moments... The noise isn't super loud but still loud enough in city traffic that there's no question that is its coming from the right front and is connected to braking. The sound kind of reminds me of when something (leafs and stuff) would gets stuck in between the mudguard and tyre of a bicycle starting making a continuous 'schooohrooooo', but a lower pitch... kind of static sounding, constant intensity.
Makes me think the caliper sticks to the rotor. But when comparing to the sounds on Youtube videos of a stuck caliper which is more of a scary screeching noise than a low pitched shroo I kind of wonder if it might be something else.
Another thing that I first suspected was a rock or some debris that had gotten stuck in between the pad and the disc, and that it found its way out by itself. But then on my second test drive the sound was there for brief moments again. So kinda rules the stone/debris problem out doesn't it, if it comes and goes like that?
The rotor which I checked when putting the studded tires one a few months ago was nice and even and now when checking after I first heard the noise there's a groove in the disc/rotor. It's about 0,5cm wide and goes evenly around the whole disc. It's rough textured to the extent that if I feel it with my finger it's definitely as if something hard that has scraped/grinded the rotor down all around. (see attached pics)
A rock or something would fit here as well, but that would not explain why I get it only now and then and also why the sound continues after braking when the brake pedal is released.
MOT inspection back in October had no comments on the brakes or their behaviour.
I haven't owned a ton of cars so first question is... should I be worried? Then... Any thoughts on this, help, ideas or similar experiences for any of you guys?