w211 Parking brake (handbrake) auto-adjuster

[selphy]

Evening all,

The parking brake shoes expanders on my 2008 E class were seizing up so I've stripped and cleaned everything and replaced discs, pads and shoes at the same time. Straight afterwards my parking brake pedal travel was really long so I had a look at WIS and tried to follow the adjustment procedure. This involves stripping out some exhaust heat shields from under the car to access the auto-adjuster which is right above the propshaft. The procedure goes something like this:

1. Remove rear wheels.
2. Set the pre-load on the adjuster (p/n A2114270841) under the car (procedure AR42.20-P-0520-01A)
3. Adjust the brake shoes using the star wheel inside the rear disc/drum. The procedure says adjust until the disc can't be turned by hand then back off by exactly 10 teeth.
4. Release the auto adjuster under the car so it takes up the slack.(AR42.20-P-0520-02A)

I followed the procedure exactly and something ain't right. When I try setting the pre-load according to the instructions the cables that run to the rear brakes are so slack that they keep falling out of their eyelets. I haven't really understood how the auto adjuster works and it seems that I must be doing something wrong.

In desperation I tried ignoring the auto-adjuster procedure and simply adjusted the star/cog wheels so that it's just possible to rotate the discs by hand. This has left me with quite a lot of pedal travel and poor parking brake effort.

Has anyone ever done this procedure? What am I doing wrong? I need to get this car through the MOT and I seem to have made it worse!

 

[Tigger]

Hi Selphy,

I had the exact same problem and wasted many hours resolving it. Seems like when you fiddle with hub mechanism cleaning it then the movement will dislodge the cables from above the propshaft.

I was struggling to relocate the cables onto the centre adjuster and had to use an allen key to hold the adjuster at its longest setting as its spring loaded. I was then able to relocate the cables.

Then you want to press the pedal down 3 clicks only and then proceed to adjust the star adjuster at each hub.

Glad you are replacing shoes like me so we shouldn't have to face this issue again for a while.

 

[selphy]

Thanks Tigger,

Good to hear that I'm not alone!

Is yours a facelift W211? WIS describes two different pedal "clicking" mechanisms - the older one with a black plastic ratchet pawl and the newer one with a grey (well actually it's white) one. It says that on the newer version the handbrake should hold on the first click of the pedal and on older versions it should be 5 clicks. I haven't seen any mention of 3 clicks then adjust the star wheels in the documentation but if that worked for you I'm going to give it a go!

I also read elsewhere on the internet that someone recommended doing up the star wheels tight, pressing the pedal down hard then tapping all the way round the drums with a (presumably rubber) hammer to centralise the shoes. There might be something it that - I do feel that the alignment of the shoes onto the backplate is somewhat hit and miss.

That cable adjuster thing behind the propshaft doesn't seem to work exactly as advertised. I think you are supposed to be able to put the allen key in, turn it half a turn counterclockwise then slide the mechanism toward the back of the car to slacken off the cable and a spring loaded detent plunger should lock it into that position so you can adjust the star cogs at the hubs with a totally slack cable. Then you release the detent plunger and the adjuster should "reset itself" and take up the slack. I think I've been misled by WIS that talks about pre-loading the cable adjuster when really you are releasing the cable tension at this point.

I will report back later, hopefully before the wind and rain starts.