I was wondering? On the rear brake caliper, there is a parking brake lever. Behind that is a rubber bushing or boot.Is fluid supposed to fill the boot up? My guess is NO! I can bleed the brake , but I can't get the brake to grab at all! That boot fills up with fluid and pop's off after 5-6 pumps. That sucks!! (Nobody carries that boot in stock,so it takes like 5 days to get). So thats when I finally thought, "maybe", there is something wrong with the seals in that parking brake "stud" assembly thingy. And that the boot was not supposed to fill up with fluid at all. And thats why the piston is not moving forward. Am I right? Also, the piston is very smooth on its sides, but the length is uneven . Is that common? Any help would be great. thanks larry

 

the rear caliper on the 500 is exactly the same as on the 250.

no the boot isn't supposed to have fluid in it at all, the seals have failed.
there are three seals on the piston, the boot being full indicates that the rear seal on the piston failed(on the pin that the e-brake presses on). the piston bing cocked unevenly in the bore may have caused it to seize, forcing more pressure on the rear seal.
to fix it, remove the caliper, take out the pads then remove the piston if possible, see if you can discover why the piston is not straight in the bore, and check it for any major damage that may prevent a good seal. remove the seals, clean the sealing surfaces, replace all three seals and any other parts necessary. put the piston & new pads in and you should be ready to go back together & bleed it. bleeding it you can leave the e-brake off to check that the rear seal is sealing properly, and adjust it after bleeding.

also check your rear brake rotor for thickness... if it's too thin, replace it.

 

thanks so much for the help. This site has graet advice!!! It worked. Thanks again, larry