I own a Mercedes W reg A class petrol model. There is a bad squeel coming from one wheel and i want to remove pads to see if there is a problem with caliper but cant work it out. can calipers be cleaned if not returning properly?

I sincerely suggest that you visit a Mercedes garage.

Capilers can be cleaned.

I do not have any information on an A class, I do know that Mercedes have been using an Active Braking system I do not know if your car has this, should your car have this active brake system you will have no choice but to go to Mercedes.

And I am not refering to ABS, that is different. With an active system you need to hook up a scan tool to tell the cars' computer to release the capilers so that you can change the brakes. If you force the caliper piston back you may damage the braking system.

How to Replace Rear Brake Pads : Removing the Parking Brake System from the Caliper