Hello Im Shawn, I have a 200 S-10 ZR2 Blazer, my brakes started to not want to release when I'd stop at a light, only once a month or so, then it got worse and worse until there it sat in my drive way rear brakes locked.

When it would sit ignition off for 30 min, the brakes would release, soon as it was running it slowly locked them tight. I read a grip of stuff on the brake system and thought it was a collapsed inner of a bake line, but then the other day I was messing around under the hood over by the relay's, where you fill the brake fluid, There is some vacuum hoses that all come together there, there are two "T's" , look at pitcher.
The one with red "x" was corroded, I put new piece on and my brakes release and my heater works better as well!