Rear caliper pistons came out as I was changing brake pad
06-29-2022, 06:55 PM
#26
Rear caliper piston came out
the same thing just happened to my 2003 mercedes e500 yesterday 😢, I was panic over some issue i was trying to figure out and I did a dumbest thing ever when I I started the vehicle and stepped on the brake pedal while everything was off the hub, so the piston came off, the fluid leaked all out I tried to put it back through the rubber seal but it was hard, so after I checked online that the rubber seals being sold separately I decided to remove the old one in order to put back the piston but the rubber seal appears to be like it is bounded to the metal, I kinda ripped it all off with no evidence that it could be removed and replaced, any idea or advice will help, I want to fix this so I can see if the main issue still exists after all the cleaning
08-21-2022, 11:22 AM
#28
Member
Bringing this back as I've gotten 3 phone calls within the past 4 days and 30+ in a couple of years. Im doing this because Im not able to answer my calls, especially late at night and I know exactly how frustrating it to not have immediate help. SOOOO here we go! DISCLAIMER: I'm not responsible for damages or injuries caused by these instructions/tips.
If your piston is loose or popped out completely...then this is for you. Im sure there are other ways to reseat the piston but this the way I put it back together and is still good as new.
1. Disconnect the brake line and E-brake wire then remove the caliper off the car
2. Set the caliper on the ground or work bench with the piston facing upward
3. Clean hands/put on glove. Pull the piston out and the CAREFULLY peel the rubber boot off. Inspect the rubber boot to insure no rip/tear/damages to the boot and lip.
4. You will now see the threaded "mushroom shape" bolt that is on a threaded shaft (e-brake motor). The top mushroom dome shape fits in the back side of the piston. Thread the bolt all the way down, this will allow for the piston the depress flat so that new pads can be installed.
5. Compress the rubber boot flat, coat the brake piston wall with DOT 4+ brake fluid, slide the rubber boot half way down the piston.
6. Loosen the bleeder valve then try to match the back side of the piston to the mushroom shape bolt, CAREFULLY reinsert the piston BY HAND and straight down, STOP and START OVER if you feel any resistant.
7. Once down, CAREFYLLY reseat the rubber boot lip (I used a pick set to guide it in the caliper slot).
8. Once step 6 and 7 are done you should be able to slide the piston all the way down, if almost done but not all the way, turn the piston so that it can slide over the mushroom shape bolt...WAAALAAA
9. Mount everything back on to spec. Bleed the brake and bleed the heck out of it as if you're flushing the line. Don't forget to top off your reservoir.
10. Mount wheel on and take it around the block slowly making sure you have brake pressure.
11. Brake menu should reset so you can do the other side, make sure all doors and hood are shut when trying to access the brake menu. The E-brake error will reset after a moderate drive
12. Check for leaks...DONE!!! YOU'RE WELCOME.
For those of you that I've helped, please feel free to add to this.
If your piston is loose or popped out completely...then this is for you. Im sure there are other ways to reseat the piston but this the way I put it back together and is still good as new.
1. Disconnect the brake line and E-brake wire then remove the caliper off the car
2. Set the caliper on the ground or work bench with the piston facing upward
3. Clean hands/put on glove. Pull the piston out and the CAREFULLY peel the rubber boot off. Inspect the rubber boot to insure no rip/tear/damages to the boot and lip.
4. You will now see the threaded "mushroom shape" bolt that is on a threaded shaft (e-brake motor). The top mushroom dome shape fits in the back side of the piston. Thread the bolt all the way down, this will allow for the piston the depress flat so that new pads can be installed.
5. Compress the rubber boot flat, coat the brake piston wall with DOT 4+ brake fluid, slide the rubber boot half way down the piston.
6. Loosen the bleeder valve then try to match the back side of the piston to the mushroom shape bolt, CAREFULLY reinsert the piston BY HAND and straight down, STOP and START OVER if you feel any resistant.
7. Once down, CAREFYLLY reseat the rubber boot lip (I used a pick set to guide it in the caliper slot).
8. Once step 6 and 7 are done you should be able to slide the piston all the way down, if almost done but not all the way, turn the piston so that it can slide over the mushroom shape bolt...WAAALAAA
9. Mount everything back on to spec. Bleed the brake and bleed the heck out of it as if you're flushing the line. Don't forget to top off your reservoir.
10. Mount wheel on and take it around the block slowly making sure you have brake pressure.
11. Brake menu should reset so you can do the other side, make sure all doors and hood are shut when trying to access the brake menu. The E-brake error will reset after a moderate drive
12. Check for leaks...DONE!!! YOU'RE WELCOME.
For those of you that I've helped, please feel free to add to this.
Last edited by JDMAP1; 08-21-2022 at 11:31 AM.
The following users liked this post:
Doubleredrolex (09-14-2022)
09-21-2023, 11:04 AM
#29
Newbie
Join Date: Sep 2023
Posts: 1
Likes: 0
Received 0 Likes
on
0 Posts
2013 ML350 Bluetec
Hi Everyone, I just did this mistake last night and this thread saved my a$$. Thank-you!
I followed JDMap1's procedure but got stuck on #7 because I couldn't force the rubber boot back into the caliper grove, the caliper got in the way.
So...I did what NDrew2013 suggested above. Put the rubber boot at the bottom of the piston (not half way up), put the boot in the caliper grove first and then push the piston down into the caliper. With everything lined up it just pushed down super easy. Boot is on perfectly.
I'll stick with being a weekend warrior mechanic from now on...not a Wednesday night one after a long day of work! I got frustrated changing break pads and started pushing random buttons, popped a caliper piston, and now get to bleed breaks. I know more about caliper piston design than I should now.
Thanks for all the help.
I followed JDMap1's procedure but got stuck on #7 because I couldn't force the rubber boot back into the caliper grove, the caliper got in the way.
So...I did what NDrew2013 suggested above. Put the rubber boot at the bottom of the piston (not half way up), put the boot in the caliper grove first and then push the piston down into the caliper. With everything lined up it just pushed down super easy. Boot is on perfectly.
I'll stick with being a weekend warrior mechanic from now on...not a Wednesday night one after a long day of work! I got frustrated changing break pads and started pushing random buttons, popped a caliper piston, and now get to bleed breaks. I know more about caliper piston design than I should now.
Thanks for all the help.
