hey there,

i just got through rebuilding front calipers and wonder if i have to bleed all four calipers or just the fronts? since i just opened the fronts, do i still have to bleed the back lines as well or is it ok to just bleed the fronts? i have abs and have already used vacuum on the fronts to get most of the air out.

by the way, i rebuilt (new piston seal, piston dust boot (a pain to get on), slide pins & associated rubbers) because even though the brake pads were done ~ 10k ago and the passenger side pads still had plenty left, the driver side were down past the center groove on the pads.
thanks

 

pretty sure you have to bleed them all. when i replaced just my rear caliper i had to do all of them.

 

With ABS brakes, you have to bleed them all. Follow the sequence in the FSM.

 

What does ABS have to do with it? If you only opened the system up at two wheels, those are the only two 'legs' of the system you need to bleed. But, if your fluid is old, it might be a good idea to bleed the other two as well.

 

The requirement to bleed all 4 wheels is because of the ABS 'Dual Proportioning Valve". In this valve is a mechanism to "balance" the pressure sent to each wheel cylinder. When you bleed a wheel cylinder, this balancing mechanism becomes mis-aligned inside the ABS unit. If you don't bleed all 4 wheels in the proper sequence so it is aligned properly, then stopping the car may result in only 2 wheels working, wheels locking up or other incorrect situations.