Does anyone know if there is any truth to a rumor I heard that with newer cars (such as my van), in order to reset the piston of the brake caliper, you must now compress the piston with the bleeder valve open? I heard that it was bad for the system to push that fluid back up through the lines, just taking the master cylinder top off...any ideas about this?

 

It is always best to bleed out any fluid from the caliper. This is the fluid that will most likely be contaminated, overheated, or generally just lost its properties. When pushing the pistons back in, open the bleeder and remove the old caliper fluid. Once the fluid is clean/clear of impurities, close bleeder, install new pads, reinstall caliper. Check fluid level in MC and move on to the next caliper.

 

Or you can push the fluid back in, and after doing both brakes do a brake flush/bleed.