Rear brake piston bottoming out. Can't assemble!

[blurple124]

Alright, brakes. I have taken the pad and rotor assembly apart 3 or 4 times since I bought my car without issue. Now I decided to rebuild my calipers and freshen the seals. The fronts went fine, they are now on the car and bled.

The rear calipers were a pain to put back together, but they are now back together and assembled in what I firmly believe to be the correct order. I used a shop manual and the mirafori guide to help me. I worked the ebrake lever a bit and the action seemed good.

Now I am trying to put the caliper back on the hangar and I can't screw the piston in far enough to get the clearance needed for final assembly. On either side. The pistons seem to be bottoming out; I can still unscrew them and they come out, though.

Same rotors, same pads, same pistons, same hangers. New seals, new brake hose.


Help is greatly appreciated.

[vandor]

Sometimes I push them gently with a C-clamp and they will go in some, then I turn them some more.
It's worth a try.

[seabeelt]

Silly question, is there fluid in them? Is the bleed screw open while you try to turn them back in?

[blurple124]

I have tried with the bleed screw closed and shut. Initially they were dry, having just been cleaned, but I tried to bleed some fluid into them in hopes that it was a lubrication issue.

[blurple124]

Lubrication was the answer! I pulled the pistons out, causing everything to be soaked in brake fluid. The once impossible-to-rotate pistons spun all the way in with ease. What a relief.

With the brakes assembled and mostly bled, I took the car out to identify any issues early on. Under heavy braking, the car pulls hard to the left, which I would guess is a bleeding issue.

This could also be related to the scraping that I heard at the front left corner. It sounds like the pads are scraping against the rotor when the brakes are not applied, as the sound goes away once brake pressure is applied. What is a good way to resolve this? Should I grease the wedges to help the calipers align better? Are the springs bad in the caliper yoke?

[azruss]

did you lightly sand the wedges and the track to get rid of any burrs. Dont use grease, use anti-seize

[wikkid]

Sil-glyde.

Available at Napa, and elsewhere. Don't work on brakes without it.

[blurple124]

did you lightly sand the wedges and the track to get rid of any burrs. Dont use grease, use anti-seize

Once upon a time I did. I will take them out again and give them a good cleaning.

There is plenty of anti-seize in the garage, so I will add that as well. I will report with the outcome.