Rahulio1975280C

Hello Everyone,

I recently acquired a 2005 C55 with ~77,000K on the odometer. I was hoping to have some pictures ready to show you all before posting but I still have not had a free weekend to really clean up the car and take my time with the photos. Hopefully I can get this done soonish.

Just have a question about the parking brake on these W203 cars.

Has anyone ever had a parking brake situation in which after releasing the parking brake, it remained just slightly engaged to the axle?
(The red 'BRAKE' light disappears when you release the parking brake.)

I have this strange feeling that it might be sticking ever so slightly. I read about some issues people have had by Googling 'w203 parking brake issue' and read a few threads on various forums about parking brakes that did not engage at all or would not release at all, but nothing really in between.

Another oddity... shortly after I purchased the car, I gave it a very quick wash in the driveway and thoroughly cleaned all the brake dust off the wheels (there was a lot of it!). After the wash, I moved it 15 feet forward into the garage for the night. In the morning I got in, started the car, shifted into Reverse.... and nothing... normally, I could just let go of the brake pedal and the car would roll backwards with the engine idling but this time nothing happened. So I decided to give just a tad of throttle and I did but the car still would not budge. Double checked that the parking brake was not engaged for some reason... it was not engaged. At least, there was no red 'BRAKE' light illuminated in the cluster. (Have no reason to use it, garage is flat!) Only after giving it slightly more throttle than I really wanted to did it break loose and start rolling backwards freely. No odd sound, it just suddenly released and started rolling backwards.

Very very strange...

Now, I do not recall ever engaging the parking brake before or after washing the car, but maybe I did for some reason.

My theories...
1. Excessive brake dust all over rear calipers and possibly all over parking brake mechanism causing it to jam or get stuck.
2. Parking brake not fully releasing for some reason, water got between pad surface and axle causing very slight surface rust which led to sticking...

From some other posts, I read that there is a small door accessible from under the rear seat bench which leads to the parking brake mechanism. This evening after a decent highway drive I tilted the rear seats forward, pulled back the sheet of sound damping and saw the small black door secured by a 10mm? nut. I touched the plate and it seemed fairly hot. Then again, it is probably very near the exhaust.

In the morning after things are all nice and cool, I am going to pop this door off and see if I can record the movement of the mechanism as I engage and release the parking brake... other than that... I am out of ideas...

Has anyone contended with a similar situation? Should I try supporting the back of the car on jack stands and try to rotate the wheels by hand while checking for abnormally high resistance?

Viper98912

Its about time you finally joined and posted something.

My guess is that rust formed on the shoes or pad and caused it to get stuck. I wouldn't worry about it if you've only gotten it once. If you feel it everytime you hop in the car to drive, then yes you might wanna check if the shoes are too tight or the caliper is sticking. Touch your wheels after a drive and see if one feels hotter than the other.

MIKESV8

yea that happens to me alot of times after i wash my car. i don't even think twice about it because i know it's from the wash. oh and just be careful when you do touch those brakes, they tend to be hot

Rahulio1975280C

Today after a 10 minute drive for errands, I touched the wheels and they all felt cool and more importantly, the same temperature. However, I then decided to touch the rotors and that is where this all comes together.

I put my pointer and middle finger tips at the 12 o'clock position on every rotor.

Front left and front right rotors, very hot to the touch, but equally hot.
Rear left rotor: warm, not hot
Rear right rotor: almost as hot as front rotors

In conclusion, I think I have a dragging or sticking rear right caliper.
I am going to pull off the wheel today and take a look at the pads to make sure they are seated properly. Otherwise I may need to replace this caliper.

DAMNIT!

Rahulio1975280C

I called the dealership to price out the part and the replacement cost if they do the labor...

$535.80 total ($374.92 for the caliper + 1 hr of labor + taxes)

Gahhhh.....

Maybe I can do this myself...

Viper98912

Since I know you and your background (alongside mine), you have no idea how disappointed I am in so many ways in your last post.

Regardless, the rear caliper is somewhat cheaply made and used across many of Mercedes' lines and years. You can find a reman unit for about $60. http://www.autopartswarehouse.com/sk...n+%26+Steering

This is all I'm gonna say for now.

Viper98912

PS - You might also want to check the tightness of your parking shoes, one of them might be just a little too tight.

Rahulio1975280C

Alright alright, time for me to fess up...

I have never done ANY brake work before, until this afternoon.
Not even bled the brakes, so removing a caliper altogether seems way above me.

This afternoon: I removed the brake pads on the right rear, and examined them and replaced them into the caliper after spraying EVERYTHING down with brake cleaner. I also put a fresh layer of brake pad paste on each side of the metal plate that sits between the back of the brake pad and the caliper cylinder.

It made no difference. There is a squeal that you would recognize from a car that is braking and has no brake pad paste. That squeal has been present before and after this operation with the car in drive and foot off the brake. If anything I gained a bit of confidence with working on replacing brake pads.

Are the parking brake shoes located closer to the passenger's side wheel? If they were dragging, would they be able heat up the right rear passenger rotor?
Can I adjust the parking brake with wheels on the car (ramps) or do I need to remove a wheel again (jack stands)?

Viper98912

The parking brake shoes are inside the hub of the rotor. Mercedes didn't leave any access holes in the backing plate, so the only way to adjust the shoes is to take off the caliper (two 16mm bolts, 5/8" works) and take the rotor off. When you open it up, you will see an adjustment star that opens and closes up how close the shoes are to the rotor. Too open and it could drag, too closed and it won't engage when you press the pedal. Everything is spring loaded, so know that if you make one side loose, the other side will take up the slack, which will cause both sides to be loose when you engage the brake. It really is a little bit of a PITA to get right, especially once you actually try to hold the car and noticed it's still loose and need to take everything off again.

Rahulio1975280C

Yeah man, especially the fronts!

Rahulio1975280C

Thank You Viper, I will be tacking this tomorrow morning.
So there is one on each side of the rear hubs, this will be fun.

Viper98912

There's only one adjustment star, the other side is where the lever and cable is located (for the pedal).

Rahulio1975280C

Ok, so there is only one adjustment star and it is located in the passenger rear hub?

EDIT: Doh, my bad, one star per set of parking brake shoes.

(4 shoes total on car, 2 per rear hub, 1 adjustment star per hub)

Viper98912

No, the driver and passenger sides are mirror images. I thought you meant on the other side of the brake shoes (across the other side of the hub, not the other side of the entire car).

Rahulio1975280C

Thanks for clearing that up.
Tomorrow I am going to pull the caliper, disc and see what the damage is, if any... if the parking shoes look normal, then I am going to go ahead and order the,

Centric brake caliper: http://www.autopartswarehouse.com/sk...n+%26+Steering

and a one man brake bleeder:
http://www.amazon.com/Motive-Product...8&sr=8-3-spell

$61.79 Caliper Base + $73.20 Caliper Core + $49.95 Brake Bleeder = $184.94 Total which is a lot less than $535.80!

Rahulio1975280C

I took some pictures when I was reinstalling the brake pads today on the passenger rear caliper.


Wheel off, fixed caliper design. (Not floating design... right?)




Weird impression left at some recent point by brake pad...


42mm caliper bore is what I think that giant "42" means...

































Tomorrow I am going to be taking this area apart again in search of a stuck or out of spec parking brake shoe.
Question: Does anyone know the torque specifications for the two 16mm caliper bolts and the 1 star pattern disc brake screw?

Thank You!

Rahulio1975280C

Rahulio1975280C

Does anyone have any tricks for getting the rotor off? I removed the star pattern set screw and have been pounding on it with a rubber mallet, but so far it just seems to be stuck on. I also tried spraying Liquid Wrench Penetrating Oil all over the lug surface, the back of the rotor where it meets the hub, etc...

So far, no joy...

Viper98912

Spray inside the lug holes (where it can seep in between the rotor and hub) and also on the front hub/rotor area. They get pretty frozen on there due to rust and it normally takes a while to get off.....

Rahulio1975280C

Thanks for the tips,

I sprayed penetrating oil in-between the rotor and hub as best I could, in all 5 lug holes, and the set screw hole. Waited 30 minutes, then tried the rubber mallet from the front and a 2x4 plus metal hammer combo to the back of the rotor. I repeated this process three times and it would not budge at all.

Since I was getting tired and really hungry. I decided to call it a day. While I had the caliper off, I pulled the pins and pads again and I noticed something I did not yesterday. The two pins that go through the caliper and the holes in the pads were extremely rough and rusty. I sprayed them down with brake cleaner, sanded them smooth with 400 grit sand paper, re-coated with MBZ pad grease and reinstalled the pads, springy bracket, and pins. Re-bolted the caliper on, got the wheel on... and...

So far, the squeal is entirely gone. I no longer have the slight resistance nor the loud shriek/squeal when coasting in idle forward or reverse.

I am going to go ahead and purchase a spare caliper, a power bleeder, and two sets of the caliper hardware kit just in case.
(The kit comes with two new pins and a new springy plate.)

This morning before I jacked up the car and started all the work, I drew on the exposed surface of the brake rotor with a Sharpie marker. Then, I put the car in neutral and pushed the car out of the garage and into the driveway. There was no evidence that the outside brake pad of the right rear caliper was dragging on the disk. So that basically left the inside brake pad or the parking brake shoes as the two remaining culprits.

My theory is that the inside brake pad was snagging on the rusty/rough pins and not traveling back with the caliper as it went back. It would remain on the surface of the rotor and would cause the shrieking/squealing sound I was hearing. Now that the pin is smooth again, the pad is able to slide with the caliper and is no longer stuck/jammed.

j21importer

for future reference the parking brake shoes can be adjusted with the caliper and rotor on. you adjust them through one of the lug holes. then you can check the feel by moving the rotor back and forth.

j21importer

and if you still have the parking brake problem it is extremely common for the adjuster to rust up and cause these issues. its located under the rear seat and is very common to fail on 203's

Newzchspy

[QUOTE=Rahulio1975280C;4359320]I took some pictures when I was reinstalling the brake pads today on the passenger rear caliper.

WOW, saw the photos above ^^^, lots of rust for a "southern car"

Viper98912

j21, that's a damn good idea, I didn't think of that. I'm used to popping out rubber caps from the backplate for adjustment, and was thinking jeez how could they not have designed this a little better. Thanks for the tip.

Newz, looks about normal to me for wear and tear brake dust and water?

Rahulio1975280C

Thanks for the tips.

Before I did all this brake experimenting, I had removed the panel underneath the rear seat and re-greased everything after a good cleaning. All of the cables and linkages were bone dry and caked with brake dust. It did not fix the problem, obviously, but at least it is one less thing to worry about for now.