What's up with Parking Brakes? - PeachParts Mercedes-Benz Forum

tivoliman · #1 04-06-2009, 10:43 AM

I understand the function and operation. Small brake shoes press against the brake drum when the car is sitting still, and in my case, the car is in Park.

Why should brake shoes ever need replaced? The wheels are not turning, so there's no wear.

The 1990 300E (about 100 K mile) and the 1995 E420 both seem to need something. Both have been adjusted, and the brake peddle still goes too far. The 300E does not seem to catch at all, and the E420 catches (that is holds the car while in neutral) but I must push the peddle very far.

Granted my mechanic replaced the parking shoes on the 560SL, and the brakes hold nice and tight. Ahhh good for the transmission.

What cause Parking Brakes to go bad?

How do you determine the cable needs replaced? Does it stretch?

Is rust something to consider? Are either the cables, hardware or shoes affected by rust? The 300E has some rust.

Pointing me to a thread that discusses how to replace them is greatly appreciated. I have a habit of putting brake shoes on backwards. Oh how I love disk brakes. Although, I suppose I could take pictures of before and after - ah the joy of digital photography.

Thanks

Kestas · #2 04-06-2009, 12:59 PM

A common reason for parking brakes to go bad is corrosion. The cables get arthritic and stop moving. Most people replace the cables. I sometimes remove the cables and give them exercise with penetrating oil, then lube them up and put them back in service.

Yes, the cables can stretch over time.

Other problems should present themselves once you've taken the rotor off.

pawoSD · #3 04-06-2009, 01:10 PM

If used regularly the wear and tear of the little bit of slippage over many uses can wear the shoes down a bit.....and they get rusty.

Also, if forgotten about and driven with them lightly rubbing, that will wear them away pretty quick. I've found they need pretty precise adjustment to work correctly.

tivoliman · #4 04-06-2009, 05:17 PM

Seems like a fairly easy job ...

Considering the age of both cars, I think I'll replace the cables and shoes in both card.

Both are W124 - which should make the second easier.

pawoSD · #5 04-06-2009, 05:27 PM

In theory they are simple to fix and replace....however in practice you will find that removal and installation of the parts will be quite a pain!

Its good to have several sizes of screw drivers, needle nose pliers, and a pick set available.

Gilly · #6 04-06-2009, 05:34 PM

There is a cable which connects to the pedal, then a seperate cable on each rear wheel. Usually just the two at the wheels seize, it's rare to need the front cable. There is also the adjuster and compensator, this is where the one front cable attach to the rear two, the adjuster and compensator also seize, it would be worth the money to check these before assuming they are bad, if you've been using your parking brake occasionally they might be fine. On the adjuster you can go by how the adjusting threads look.
Along with the parking shoes you can buy the hardware kit, that's usually pretty cheap. The pivot, which is the piece inside the drums (rotors, whatever) is often siezed, I believe this would come with the hardware kit. The most common seized part is that pivot and the pin that connects the pivot to the cable end.
Are you sure you are adjusting the parking brake correctly? First you loosen the cbale adjuster, then there is the "star" adjuster you get at through a bolt hole through the rotor and hub, (you need to look up the adustment procedure or I can get "in" to it more), then the cable adjuster is retightened, then check for evenness side to side.

Gilly

tivoliman · #7 04-06-2009, 07:42 PM

I checked the cable and adjusted by the cable splitter (right left) but the 300E was still not right.

But I did not check the moving parts in the shoe area - may have seized

The front cable is moving.

Noticed the hoe kit has springs nut not the other stuff.

How do you suggest I clean the rust and such near the brake shoes? (inside the drum)

Gilly · #8 04-06-2009, 08:13 PM

The cable end is the part that holds most of the rust. Once you get it all disassembled, you can wash it like the insides of the brake caliper, such as a small wire brush and brake clean type spray-on product.
Hard part, if things are seized, is getting the pivot off the end of the cable.
Gilly

cliffmac · #9 04-06-2009, 09:32 PM

you should never have to replace the parking brake....ever

Gilly · #10 04-07-2009, 04:42 AM

That's why dealers have all the parts in stock

david s poole · #11 04-07-2009, 01:47 PM

the main reason park/emergency brakes get worn out is because some blind dodo couldn't see the red brake light on the dash and drove with the brakes on thinking that the car was a little sluggish today.

compu_85 · #12 04-07-2009, 02:55 PM

The repair manual suggested driving for a short distance with the brake on every so often to clear rust. I did this on my car when I first got it and it improved the pbrake.

-J