I have an 06 Just a Cooper. I ran into a problem today. I heard a disk brake squeel from the passenger rear. I pulled the caliper and pads off and decided to replace the pads. I noticed the boot around the caliper piston was torn. Now I have two questions. I can't get the piston back into the caliper in order to get clearance for the new pads. I tried turning it clockwise many times and it did spin but it would not move inward. What should I do? The other question is can I replace the boot itself without buying a caliper?

 

I haven't worked on a MINI rear caliper but my experience with my other car is if you have a torn caliper piston boot is to check the piston for corrosion when you remove it. Any piston corrosion can scratch the seals if pushed back in and you can get brake fluid leakage. I bought a new piston, seal and boot and rebuilt the caliper myself which was time consuming and messy.

Having said that, it's a whole lot easier and not that much more expensive just to buy rebuilt calipers depending on what needs replacing. If you only need the boot, caliper rebuild kits from rockauto are less than $5.

 

You have to push and turn at the same time. They make a special tool that makes it easier, I just use a pair of needle nose pliers. The last time I did it, it seemed to spin for quite a while without retracting - just have to push when turning. Once it starts going, it goes pretty quickly. You should be able to source a dust boot.
http://www.pelicanparts.com/catalog/...BRKhyd_pg1.htm

As Ray said, you want to check and make sure there isn't any corrosion.