Brake caliper piston boot bulge?

[zanzarista]

This past weekend, I changed the pads on the rear. I noticed that after I slowly pressed the caliper piston back into the caliper, the rubber boot that surrounds the caliper piston didn't sit nicely into it's groove. The rubber boot has a small bulge.
I tried using a vacuum gun to pull fluid from the resevoir to get it to go down. I also tried re-extended the piston to it's (extended) limits by pulling on it slowly and then opening the drain and pushing the piston back in.
I found that you can get it pressed back into place and it will stay for about 15 seconds then it will extend out slightly. Sometimes, I found that I ended up chasing the bulge around in a circle, as I pressed on the bulge in one spot it would spring up in another!

So the real question is why is it bulging and is this a problem that needs to be addressed? Is this one of those things that the brake piston was extended for so long that the rubber took on a set due to heat?
No, I didn't take pictures....

I've already reassembled the brakes and they work as good as new.

Thanks for your assistance.

[Layspeed]

Sounds like a little air pocket developed between the piston and the seal/boot. Just carefully take a small screwdriver and pry under the edge of the seal and lift the seal away from the piston. It should sit nicely then. I see it a lot at work...haven't seen it be a problem, as long as it doesn't tear the seal.