HELP! Pistons came out too far and won't go back in
Thread Starter
Newbie
Joined: Feb 2018
Posts: 3
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C300 4Matic
HELP! Pistons came out too far and won't go back in
I messed up trying to replace my pads and rotors today. I removed both the rotors and pads for the fronts at the same time. While I was putting everything back on the driver side, I went in the car the pump the brakes to test out the compression. I later only realized it pushed out the pistons really far out on the passenger side. I tried using a c-clamp and also remove the bleeder valve and it still does not go back in.
Any help on what I should do?? Thanks in advance!
Any help on what I should do?? Thanks in advance!
Junior Member
Joined: Jun 2008
Posts: 23
Likes: 4
2014 C300-4M
If the piston had uneven pressure on it when you pushed the pedal, if may have canted to one side. It won't go back in at an angle, it has to go back in exactly straight. I would try to align it first and compress it without impact, using whatever you have. Vise, clamp, pliers, dungeon torture devices - whatever's handy. If not, I've used a rubber or plastic headed mallet and a piece of scrap wood to negotiate stuck pistons with some success. If you impact it to get it back into place, you may deform the piston and the cylinder, which would necessitate a new or rebuilt caliper. Hope you get it squared.
Thread Starter
Newbie
Joined: Feb 2018
Posts: 3
Likes: 0
C300 4Matic
Thanks @JustLooking. I ended up flushing all of the brake fluid from the line and I was able to compress it back in by hand. I then bled the line to all of the brakes. It's working perfectly now.
