The only way a piston can come out is if you apply brake pressure with the caliper off the car and he pads removed.

Not too sure I would suggest YOU try and fix it.

Me, I''d just pop them back in but I've rebuilt hundreds of calipers so know what to do.

I suggest you get help.

 

 

Did you put the car/brakes into service mode before removing the rear brakes?

I know it won't help now, and I have no personal experience regarding this, but I've read that there is a service mode you have to put the car into when replacing the rear brakes. When it's in service mode the car retracts the rear pistons to allow you to replace the pads. I'm assuming if it wasn't in this mode then either you wouldn't have been able to remove the pads, or if you managed to remove the pads the car is maybe applying pressure and pushed out the piston.

Again no professional knowledge/experience here but if they just popped out I would clean everything up in case it got dirty from falling out, make sure it's lubricated and then just pop it back in.

Don't forget to check/top up your brake fluid level after its popped back in, some could've flowed/leaked out when the piston came out.

 

Yes, there is a command procedure that retracts the rear caliper pistons (which are used by the electric parking brake) that needs to be performed before changing rear pads that clearly wasn't followed.

If you know what you're doing - and with respect, you don't appear to seeing as you're posting this here - you'll need new seals and boots, some silicone grease, about a liter and half of fresh brake fluid and a pressure bleeder to bleed the brake system. Furthermore, seeing as the piston retract procedure wasn't followed, I am not sure that you can now perform the same using the usual procedure so I'd probably have the car towed to someone who knows what they are doing.

 

You can't just pop them back in. The parking brake motor is still in the "normal" extended position and the car's control module also doesn't know that the brakes have been removed. You also can't simply check and top up the brake fluid as there's now air in the system and you need to flush and bleed the whole thing. Judging by the color of the brake fluid, it would have needed to be replaced regardless as it looks burnt.

 

Did you ever get this fixed

 

Going thru this same issue right now

 

Guys, here’s the drill. I’m gonna oversimplify it because I want to give you broad strokes of how to fix this and some cautions.

Once you have completed the rear brake retraction via the key to position two, phone buttons and OK button, then:

Remove the rubber dust shield from the caliper. Make note of the orientation of it. Apply the dust cover to the outer ring of the piston.

Line up the piston with the cavity, re-seat the dust boot and begin to press EVENLY to not let the piston go in crooked. And I mean ZERO angle. A little brake fluid around the outside of the piston won’t hurt.

Once the piston is in as far as you can get it by hand, replace the pad and use a c-clamp or other device to press the piston all the way into the cavity.

Reassemble the brakes and remember you now have a **** ton of air in the lines. You MUST do a bleed after this now.

Good luck, it’s really not bad since it’s a single piston sliding setup. A whole lot more fun with 4/6/8 piston calipers ��

 

Was there a certain sequence that you have to use while bleeding the brakes?

 

Usually with most cars, it begins with the caliper furthest from the master cylinder. So RR, LR, RF, LF.

And with dual bleed nipples, start with inside first, then outside.

 

Suck old Fluid from main cylinder, add fresh and start from the farthest from the main cylinder, which is rear passenger side, rear driver side, front passenger and front driver side. At least this how I do it.

 

I appreciate you sharing that information, saved me. not sure why I pushed the park brake with everything disassembled but I did, and knew it was a mistaken immediately. Life just has to at times beat you down to allow you to be built back up. .for me that will be the passenger side that hopefully takes all of 30 minutes compared to my 4 hours tonight. Thank you

 

Bringing up old thread here. Anyone who has solved this issue please give me a call 405-205-6556. I'm a little defeated from the piston not wanting to go back in and don't know what to do next. Also my MB menu is not allowing me to put it in "changing pad" mode. I've literally got both rear calipers apart in my garage. PLEASE HELP!!

 

Hi, I was wondering if you ever got your issue resolved in your car?? Have the same issue and could use some advice!

 

I got it solved and now good as new. Holler at me if you have any issue.

 

call me. 4052056556

 

changing rear pads and rotors on 2015 s63 sedan.
easy enough... or so I thought
Daughter asked if she could help (6 years old) always let her give a hand when working on teh AMG's but boy, this was a mistake.
Going through Ebrake release... she pushed instead of pulled, as that was the one item I was going to let her do..... ebrake screwed the pistons right out of the caliper...lol

So, my techs at MB in Orlando, never seen this, suggest only replacing caliper is only way to go.
This single piston caliper looks so simple mechanically, that I believe I can fix this myself and get seals to reseat, as nothing looks torn or ripped?

Did any of you actually have success in pushing this back in, and bleeding system and not developing any issues?

Seems the screw for the ebrake is easy enough to screw right back in, then just reseating the piston is a bit difficult, but opening up the bleed valves etc surely helps with that, especially since I will need to flush entire system now anyways.

Anyways, bringing this current, as changing pads and rotors are so damn expensive at the Stealer, figured many are resorting to doing these easy jobs themselves to save a couple grand on labor.
The Ebrake release (or rather not activating Ebrake once caliper is off) is so important, I do plan on posting some youtube videos to warn others of the importance of this Ebrake Dilemma as I don't think it is warned enough.
My main problem was not doing this simple release prior to starting the brake job.
Once calipers are off, there is no room for error on this move.

 

Yeah... I am sure many S63 owners find brake jobs at the "Stealer" expensive, and are no doubt doing their own brake jobs and everything else they can to avoid being ripped off (not to mention wasting their time posting on an online forum). I am sure there are some brake job savings coupons you can find on the S-class forum (hint - this isn't it). You're already on the right track by attempting to use child labour though.

 

Haha... i hint the sarcasm... but in reality, my kids know more about vehicle mechanics now than most grown adults due to the responsiblities I put on them when we mainteance our AMG collection. I actually never allow anyone to work on any of my vehicles including dealer if I don't absolutely have to, and even when I do take it there, I only allow 2 specific mechanics to work on them.. but even then... everytime I take this car into a dealer, I get it back with Scratched or damaged carbon dash inlays, dings in qtr, recnetly scratch on rear bumper, not to mention the last two times I took car in for warranty items, it just sat their for weeks, when I could have fixed the issues in a much quicker time frame.

So I very much try to take all maintenance items into my own hands. Sure, the w222 model is a bit more sophisticated than all my prior collection and other vehicles on hand, but nothing that can't be tackled. Being very mechainically inclined, brakes jobs are about as easy as maintenance jobs get. Of course I never thought daugher would possibly push lightly rather than just pull the handle. At least she is now getting experience in rebuilding some simple TRW calipers.

And this is when all the professionals and mechanics state I have to buy new calipers, this is just not true. Ill show them a 6 year old rebuiding them and send them the How To youtube video later so they also will know how to do this.

Just about done putting these things back together properly, and don't foresee any other issues in completing this job.
Ill post a how to as I searched it seems many have this simple ebrake issue on the rear calipers across the country and different forums.
And thank you to the members that reached out to provide simple solutions, and it just confirmed my thoughts on how uncomplicated this caliper truly is.

Simple simple, but when you don't know, you just dont know.
Thanks all,

 

If the S uses the same or similar rear brake caliper with integrated parking brake as the ML, there is a procedure that you have to execute before changing the rear pads that retracts the rear caliper pistons. I unfortunately don't know if this is even possible once the calipers have been disconnected and removed, although I suspect it wouldn't hurt to try to at least retract the parking brake motor in the caliper so you can put the piston back in.

I've rebuilt race brake calipers before, but I have no experience with the single-piston calipers with the integrated e-brake. If you Google it you will find references to the key combination you need to press to get to the piston retraction menu, and, all joking aside, I would suggest you search for the ML as I really don't think many S class owners are doing their own car maintenance. Good luck!

 

Hello everyone,
Sorry for delay in response. I was able to rebuild both my rear calipers on my S63 w222. unfortunately on my first caliper attempt, I did rip the original piston seal. So I ordered some new calipers just in case, while I searched for a solution. Well after buying about 20 various rear brake piston seals from various manufacturers that build replacement seals for the TRW calipers, i was able to locate one that was about an exact match. that would be the Dorman Piston Seal, part number D351562. It is identical in just about all aspects.

Well I installed back around May 5th, have put over 1000 grueling miles and brake tests on the car to make sure no issues, and glad to say I was able to return and restock both the rear calipers I had purchased saving me a ton of money.

The replacement seal only cost me $11 bucks, and works good as factory.
after all built and reattached, no issues, warnings or lights.
just be sure to Bleed the crap out of your system, i use a motive self bleeding system.

So now we don't need to worry about this Ebrake issue, as it seems common, and now not that big a deal. just take all apart, reset the Ebrake screw manually with a screw driver, put on new piston seal and slide piston back in caliper, and you are good to go. If using your original seals after this event, I may recommend some engine assembly lube or other very slick lubricant just to help not rip an old or used seal while reinstalling.

Anyways, hope this can help a ton of people, and this is a now a very cheap fix.
the best part about it, is I made my 6 year old daughter fix the last piston, since she hit that ebrake button originally...haha.
So yes, my 6 year old is back on top of her game with her new caliper rebuild skills on the AMG platforms.

these are both seals stacked on top of each other

side by side, original torn on left, new on right. only real differnce is the folds are a bit more squared than round on outside face. I stretched both out to make sure both can get to full extraction etc. all good

installed

dorman box and part number


happy to answer any other questions

 

Hi do you twist in while you compessing the piston?
im having difficulty putting piston back since i dont have special tool

 

I actually used a bit of engine assembly lube to help me slide my pistons in originally. Make sure the bleeder valve is open while you push piston back in. make sure the electronic brake screw is fully retracted. If you find that your piston starts to bind, it is normally due to it starting to angle. if this happens, you can screw the electronic brake screw out towards the back of the piston to help it seat, and may help straighten your piston.
Just simply remove the electronic screw motor off the caliper and set it aside. then you can gain access to the back of the screw and turn it manually.
then you will have to slowly retract that screw as you push piston in. Also, to hold my caliper perfectly level, I vised my calipers to hold them steady, then used a small peice of wood on top of piston. once my hands were free and piston and caliper were secure, it allow me to put my body weight direclty over the piston in a downward motion, and slid right in. prior to all these steps, it felt almost impossible to get piston back in, either becuase i could not get it perfectly straight or i could not put enough weight on it without binding due to an angle issue. I did not twist at all. Did not have any special tools nor did i need them. just vise, wood, prybar, etc. The S63 is still going strong after another 4k very fast and hard braking miles since I got these back together, and all working perfectly.

 

This thread saved my butt. Being a dumbass, I found myself with the caliper piston falling out and brake fluid all over my garage floor. I was feeling pretty dejected until I found this thread and was able to get everything fixed. Thank you jkintegra and jetpilot718 for taking the time to post guidance on this topic!