WinterPark321

Hello, for all of you wondering how to do your X166 GL550, here it is:

Items you will need:
Mercedes Disc Brake Pad Rear - Genuine Mercedes 0074207820
https://www.fcpeuro.com/products/mer...mer-0074207820

Mercedes-Benz 211 540 17 17, Disc Brake Pad Wear Sensor


*13 mm socket
*11/16 in open-end hex wrench or 17mm. I used 11/16 because I did not have 17mm.
*Wire brush

In order to do a brake pad replacement on these cars, especially those with electronic parking brakes, you MUST follow step 1 carefully. Basically, when you get to removing the caliper, you will see that there is an electronic module connected. This, I am assuming is the brake-assist feature, therefore one must disable the module in order to replace the pads or else the piston will not be able to push in. If you try hard enough you WILL BREAK the piston.

1. To make the piston is able to be pushed back in:

• put the key in position 1 (for those with push-start feature, push the start button once, without holding the brake)
• If not already, toggle to the page with the mile/trip odometer
• Press and hold the "call button" on the right side and simultaneously press and hold the "OK" button on the left side until the service menu pops up.
• 
  
  Hold these buttons for service menu (2013 GL550)
  
• Select "Pad replacement"'
• Select "ok to disengage brake". - (Note: After disengaging brake pads, it is ok to leave the car in position one as car will shut off after a while (if you have the push-start feature). once finished with brake pad replacement, you can turn to position one again and the pad replacement menu will automatically appear)
• Once finished with brake pad replacement, press ok again to re-engage brakes.

Continue on replacing pads as usual.


2.Jack vehicle up using the jack points.
3. Remove wheel
4. Remove the 13mm bolts on back of caliper.
5. If step one was done successfully, caliper should be able to be wiggled loose and stored on top of rotor. For safety, you could bungee cord the caliper. I just found a perfect position where caliper was secure. (Sorry forgot to take photos). Then, remove pads
6. Wire brush caliper, and caliper bracket for brake dust
7. Change pads, and also brake pad sensor if you're doing the passenger rear wheel. (If you had bought the kit above, there should have been new retaining clips provided too. Those just pop out.)
8. Reassemble caliper. (If you had bought the kit above new 13mm screws should have been provided too. Throw the old ones out and install the new ones. Doesn't hurt to have new screws)
9. Reassemble wheel.
10. Once finished with brake pad replacement, press ok again to re-engage brakes. If car had turned off, press start button or turn to position 1 to re-engage brakes. DO NOT DRIVE THE CAR WITHOUT DISABLING "PAD REPLACEMENT" OPTION

Happy New Year!

novae500

Need some help. Foillowed the steps of the dash and disabled the parking brake. Undid the 13mm bolts and able to remove caliper, remove old pads, iinstalled new pads. BUT, As i used my tool and lined up the disk to the piston and turn the tool handle clockwise, the piston just spins and doesnt recess slowly back to allow enough clearance for the new pads. What would cause the piston to just spin and spin but not go back flush to give clearance to go over the new pads???

mtm

The piston doesn't retract by rotation. Put an old pad over it and use a clamp or a lever to push it in.

novae500

Thanks, got it to work and pushed it in and went in with out much resistance. Did passenger side left and to clean the caliper bracket enough to wear it could be pushed recessed in. Now have some new pads on the rears.