Occasionally when i'm driving my brakes are squeaking and squealing, goes away when i turn the wheel but soon as i straighten up again squeak squeak. How can i tell which caliper is sticking?

I need new rear disks and pads but i know that won't affect the fronts. I found a receipt in the car for a caliper replacement on the passenger side before i got the car, so could it be the other caliper now? It's driving me mad as my brakes are squeaking when in use aswell! :(

Is it just a case of stripping the calipers off cleaning them and sanding the pads to get rid of any glazing or am i looking at a new caliper?

If it's a caliper do they come already done green?

well you can tell if its front or rear by applying the handbrake when it next makes the noise, if it stops its the rear, then its a case of jacking it up and seeing which is sticking

I spoke to one of the mechanics at work today and he's said it's a high possibility that it's my rear disks and pads as they are basically metal to metal right now

But I'll try doing the handbrake method anyways