I went to go change the brakes on my '01 F4i, and once I took the old pads out and tried to put the new ones in, I realized the piston had moved forward (inward towards the pads) so much that I couldn't fit the new pads in. I tried pushing the piston back as hard as I could but it won't budge. It will still move farther forward (inward) when I press the brake pedal, so I don't think its seized. How can I get it to go back in so I can install the new pads? Do I need to flush the lines?

 

There is a special tool you can get at most auto parts stores. Its for compressing the piston back into the caliper. The tool is inexpensive and helps ensure that you're pushing the piston straight back into the caliper. Sometimes it's necessary to open the bleeder valve in order to get the piston to go back in.

Since you're at the point where you're needing to replace your brake pads, I would certainly suggest that you flush the old brake fluid with new fluid. If the fluid looks a little brown, it's time.

A tool similar to this is what I'm referring to.

 

Dirts advise is perfect. A little trick I always use. Place old brake pad back in caliper, with a pair of channel locks SLOWLY squeeze until piston is totally closed, install new pads, and put back together. You may as dirt said need to crack bleeder but usually I just open brake fluid resevar(wrong spelling ) and if it is full take out some fluid BEFORE compressing caliper. Another trick to use on 2,3,4 piston calipers is a C- clamp w/ the same procedure. Good luck, ED

 

Thanks for the advice guys. I opened up the fluid reservoir and after cleaning some gunk off the piston, was able to push it back in. I have since flushed the rear brake and cleaned off the piston, and it now works flawlessly.

 

Sweet, glad it worked out.