I have a 2000 sierra and need to replace the pads. I got a manual and it says to remove the bleed screw before compressing the piston back into place and I am curious as to why. It says that only ABS systems need to do that. Is this something that is specific to GMC vehicles because I replaced the brakes on my cutlass supreme and did not have to remove the bleed screw and it was ABS too. Any thoughts would be greatly appreciated.

 

Its just precautonary..They don't want any dirt,debris,etc "backing up" into the abs...

 

I would say its b/c the hcu(a series of solenoids that pulse your brakes hundreds of times per second) would not allow the piston in the caliper to push fluid back into the resevoir. therefor by cracking the bleeder you are allowing the pressure to be vented and you wont risk cracking or breaging anything..remember up to 3000 psi in a brake system.

ps..top off resevoir after doing this