How can you tell if the Caliper or Piston is bad? It looks like the rear brake on my 99 Forester isn't working. The rotor is dull and after driving a few miles was cold.

Could be air in the system. Put it on jacks and have someone step on the brake for you, can you turn the wheel?

 

If so, you are not getting pressure to the caliper or its frozen solid. I'd start with a good brake system flush.

 

How many miles are on it?

134,000

In the past I had problems with the breaks overheating because the pads fit to tight in the channels.

The rears never seem to get much wear. Calipers usually get stuck out. They usually have a lot of pressure pushing them out. But not much pressure when they retract. Infact on my old VW's I've had the rubber hose deteriorate to the point that it causes this issue.

 

I'd pull the bracket that the pads ride in as was suggested. File the bracket (after removing the stainless clips) to remove rust, reinstall clips. Then see how well the pads ride on those clips. Even new pads often need a little work with the file to get them to move easy enough. I add some anti-seize as well.

 

Going into this I'd think the caliper wouldn't be the most likely issue. You may be able to get an idea if it's totally frozen by trying to compress it.

I'll second the cleaning & lubing. In our shop we don't do ANY brake job without removing the bracket (when possible) and glass blasting where the pads ride, or cleaning/filing non-removable brackets. Lube up the sliding surfaces with high temp brake grease, and make sure the pads fit nicely and can move easily. If they stick, file the pads slightly to let them move easier. The shouldn't be really loose, but should move freely.

 

I really hate to see cars that have brake work done at the large major chains (in our town the worse offender is Midas). They never clean anything, never lube anything, and just slap things back together. I have even seen cars come into our shop with actual hammer marks on the pads because they went into the slides hard, and the other shop just pounded them in!

 

Jim

Thanks for the info everyone, I will start with a good cleaning and lube.