W210 Parking Brake Fail & Fix - PeachParts Mercedes-Benz Forum

anghrist · #1 02-10-2013, 07:11 PM

This one had me a bit perplexed folks.

My parking brake has been inop for a few months, and I had no idea why.

There was something that had obviously gotten stuck, the symptoms:

1) Parking brake release handle sticking out, but still connected.
2) Parking brake pedal made ratcheting clicks, and was solid, but would not lock in place.
3) When pressure released from pedal, pedal returns to released position.

So I finally pulled the driver's side lower dashboard cover off to see what was happening. The first challenge here was to get the darned cover off from around the pedals and such. If no one has done this it's not too bad, just:

#1 Use philips screwdriver to unlock the driver's footwell vent (the black vent on the central tranny tunnel).
#2 Pull the vent out with your fingers by gently prying the back away from the carpet, then slide the vent toward the rear of the car.
#3 Unscrew the three retaining screws on the dashboard underpan (2x are on the velour cushioned portion and one is on the black plastic at the doorframe.
#4 Unscrew the plastic retaining nut/flange from the firewall near the accelerator pedal.
#5 Pull the hood/bonnet release and disconnect the cable from the handle. (pull some slack in the cable and slide the retainer bead out of its socket)
#6 Unscrew the retaining screw for the hood/bonnet release handle.
#7 Using a plastic wedge, pry the lower panel away from the dashboard in the following places:
- Put the wedge under the velour panel and pry along the vertical edge near the park brake handle (pry straight out)
- Pry the velour panel straight back to unhook the panel from the black plastic steering surround.
- Pry down and to the side slightly on the lower left side of the steering column to release the retainer clip.
- Pry straight down just to the right of the steering column under the velour panel & pull straight down on the bottom edge of the velour panel where it connects to the center console on the transmission tunnel.
#8 Once the panel is loose, remove the hood/bonnet release lever and slide the OBD-II socket retainer to the right of the car and pull the socket out of the panel.
#9 gently work the panel out of the footwell and move it out of the way.

Now you can get to the parking brake pedal mechanism.

There is a black cover that just clips to the very front and rear of the assembly. There is also a bundle of wires zip-tied to the top of this cover. I recommend carefully cutting the zip tie and moving the entire cover out of the way.

Next I checked the cable that actuates the parking brake release. It was still intact and connected at the handle and the top/rear of the assembly (nearest the firewall). The problem was that the release was being held 'open' and here's why:

If you look closely, the return spring for the release is fully extended. What has gone wrong here is that the metal retainer (in the blue circle) has slipped out of place and is now holding the release fully open. Don't ask me how this happened. I haven't a good answer.

The metal retainer must be relocated back into position in the slot in the black plastic release 'lever' located toward the pedal pivot shaft. This image shows the proper position of the metal retainer:

Notice that the release 'level' is now in the closed position and the return spring is again compressed.

Here's a quick video of this portion of the pedal mechanism in action:
W210 Parking Brake - YouTube

Once all is well, reassembly is reverse of the above instructions.

I also recommend putting a little grease on the steering shaft down where the rubber boot is located. That will keep it quiet for a while.

pimpernell · #2 02-11-2013, 11:43 AM

As for the spring coming off, I know on my 96E300d that under the rear seat there is a part of the emergency brake mechanism covered by a metal cover. Underneath the cover was a swivel device that the cable was connected to. If that device is slow to activate or binding, and fails to take up the slack when the pedal is released I think it could be possible for the spring to unhook at the location you indicated. Just a guess on my part, and thanks for the write up.