PSA: Going into fitment mode while rear caliper is off the rotor and fix
12-10-2021, 07:31 AM
#1
Super Member
Thread Starter
PSA: Going into fitment mode while rear caliper is off the rotor and fix
First of all, do not and I mean DO NOT put your C into brake fitment mode when the caliper is off the rotor. If you forgot to put it into fitment mode and pulled the caliper off, you’re better off by putting the caliper back with the old pads and then set the mode.
I forgot to put my C into brake fitment/service mode before pulling the caliper off the rotor. I then performed the fitment mode while the caliper is off the rotor. The piston extended way beyond its norm and would not retract using C clamp or caliper press tool. I also opened the bleeder valve and press without any success. After 3-4 hours of trying various methods and Google the net, I found that the piston would retract by turning the parking brake motor gear shaft (clockwise I think) with a vise grip when the piston is stuck then pressing the piston with the caliper press. This turn and press procedure took a little over half hour. The gear shaft could be access by pulling the parking brake motor off the back of the piston by taking off the motor cover and unscrewed two mounting Allen screws.
Thought I post this to help other unfortunate souls.
I forgot to put my C into brake fitment/service mode before pulling the caliper off the rotor. I then performed the fitment mode while the caliper is off the rotor. The piston extended way beyond its norm and would not retract using C clamp or caliper press tool. I also opened the bleeder valve and press without any success. After 3-4 hours of trying various methods and Google the net, I found that the piston would retract by turning the parking brake motor gear shaft (clockwise I think) with a vise grip when the piston is stuck then pressing the piston with the caliper press. This turn and press procedure took a little over half hour. The gear shaft could be access by pulling the parking brake motor off the back of the piston by taking off the motor cover and unscrewed two mounting Allen screws.
Thought I post this to help other unfortunate souls.
Last edited by miketc; 12-10-2021 at 07:34 AM.
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Greg52 (12-14-2021)
12-15-2021, 02:35 PM
#2
Newbie
A few months ago I made this same mistake and it cost me. In 2015 they started putting electric parking brakes on the rear. I knew about resetting the service mode through the steering wheel controls but I was unable to retract the rear pads. I later figured out that problem was caused because I had my door open. All your doors and hood have to be shut before you reset anything. Anyway, I pulled the rear caliper off and the piston came out as far as it would go. I could not press it back in with a caliper tool and I took that cover off the parking brake motor and was unsuccessful in turning the gears back manually. I finally got a hold of a Mercedes mechanic and was told I would have to buy a new caliper, that cost me $300. I put it back together with no problem. Those electric rear parking brakes have to be retracted using the steering wheel controls before you start working on them. I have done brake jobs for 45 years and I thought it would be easy.
Last edited by C3004matidriver; 12-15-2021 at 02:45 PM.
