Main.TrailIndexPage | Brake System | Hand Brake

Hand Brake

This component is part of Brake System.

Definition

The Hand Brake (handbremse), or parking brake, or emergency brake, is a mechanical system used to apply the rear brakes for parking or in the event that the main hydraulic brake system fails. The hand brake is mounted on the transmission tunnel. The one piece handle 1 is painted black, but the grip area is chrome plated. A rubber grommet 3 covers the transition from paint to chrome. The adjusting nut 27 is also chrome.

Function

Referring to the Hand Brake Component Diagram above, pulling up on the hand brake 1 pulls the front brake cable 25, which pulls the equalizer 30 forward against the pressure of the return spring 33. The equalizer balances the pull between the left and right rear brake cables 35 and 36. On the 230SL the rear brake cables expand the rear brake shoes against the drums, while on the 250/280SL they operate on a smaller drum and brake shoe system on the outside of the disc brakes. A pawl 4 engages a toothed section 15 to hold the brake shoes in the expanded position against the pressure of the return spring. Depressing the thumb button 11 disengages the pawl, and releases the brake.


Procedures

Please refer to the numbers in the technical diagram above


Removal & Installation

Hand Brake Removal

  1. With the brake in the down position, unscrew the adjusting nut 10 and remove it from the front brake cable 9. Use a 5mm rod or small bolt to help turn the nut if needed.
  2. Unscrew the pivot bolt 5 but note it is a left hand thread and unscrews clockwise
  3. Depress the thumb button 1 to disengage the pawl 3 and pull the handle forward to remove.

Hand Brake Installation

  1. Loosen the bolt 6 that holds the toothed segment 4 to the transmission tunnel.
  2. Depress the thumb button 1 to open the pawl 3 and slide the brake lever over the toothed segment.
  3. Lubricate the pivot bolt 5 with grease and screw into the transmission tunnel.
  4. Tighten bolt 6 and check brake lever for freedom of movement.
  5. Insert the front brake cable 9 into the brake lever 2.
  6. Make sure the offset portion of the front brake cable is toward the front of the car and attach the adjusting nut 10 and adjust per the instructions below.

Adjustment

Hand Brake Adjustment

  1. The pawl 3 should engage 3 of the 6 teeth of the toothed segment 4 with a strong pull.
  2. If the brake lever pulls up higher than that, lower it to horizontal and turn the adjusting nut 10 clockwise to tighten.
  3. If the adjusting nut does not provide enough adjustment, the brake shoes will need to be adjusted, see below.

Hand Brake Shoes (250/280 SL with rear disc brakes)

On 230 SLs with rear brake drums, the rear brake shoes are also used for the emergency brakes but operated by the hand brake cables. On the 250/280 SLs with rear disc brakes, the hand brake/ emergengy brake uses two small brake shoes housed inside the rear brake disc. The inner part of the brake disc hub acts as a brake drum for the emergency brakes. Operation is also by brake cables, however they are not interchangeable with the 230 SL cables.

Here is a photo all the emergency brake parts;

Two special tools will make the job quite a bit easier. One can easily be home made, the other is an inexpensive spring tool. Grind a round screwdriver shaft or similar for the home made tool.

Use the home made tool to release the retainer springs first. Push in then do a quarter twist to release. The retainer spring hooks through the hole in the backing plate see photo of the back view.

After both retainer springs are removed use a large screwdriver to pry the top brake shoe far enough to remove the adjuster. this will loosen up the entire assembly enough so that you can remove both upper and lower return springs with the spring tool.

Both emergency brake tools can now be remved. Next remove the cam assembly by pushing the connecting pin out.

There is a special "C" clip which must be removed before the emergency brake cable can be dis-connected from the backing plate.

Continue the axle removal by unfastening the 13mm nuts around the axle.

My re-installation of the emergency brake assembly is the reverse order of above. I prefere to deviate from the factory assembly sequence in that I install the brake adjuster and top return spring last instead of first.

Brake Shoe Adjustment

Note this is for the 250/280 SL only which have a small drum brake on the outside of the rear disc brakes. The hand brake on the 230 SL operates the standard rear drum brakes, see ___ .

  1. Remove the hubcaps and one wheel lug from both rear wheels.
  2. Jack up the back of the car and place on jack stands so both rear tires are off the ground.
  3. Turn the left wheel so the lug hole is 45 from straight up, toward the rear of the car (about 1:30 on a clock).
  4. Look through the hole with a flashlight for the toothed brake adjusting wheel.
  5. Insert a long thin screwdriver through the hole and adjust the wheel with an upward motion until the brake shoe touches the drum and the locks the rear wheel.
  6. Back the brake show off with a downward motion about 2 or 3 notches until the wheel spins freely.
  7. Repeat for the right wheel with the following important changes
    • The lug hole is 45 from straight up, toward the rear of the car (about 10:30 on a clock for the right wheel).
    • Move the screwdriver downward to tighten and upward to loosen.
  8. Test by making sure the wheels still turns freely when the hand brake is engaged 1 notch.
  9. Adjust the brake shoes if necessary.
  10. Adjust the hand brake if necessary as shown above.

Maintenance


Old Yahoo content

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The emergency brake cables should be greased. Inactive calipers can also stick. Old rubber brake hoses can become restricted and also lock brakes by not allowing fluid to return. If your emergency brake handle does not have the normal feel then a cable is probably sticking. The brakes are meant to take a lot of heat. Brief overheating will not usually cause additional problems, as long as the problem is fixed. To keep everything in good working order, try to drive the car every month or two even during the winter on nice dry days. Do not just start it take it out and exercise all the systems. Also change the brake fluid every two or three years. Use Castrol, ATE, Mercedes or another good grade fluid. Cheap domestic substitutes can shorten the life of rubber parts in the brake system, especially on the earlier cars. The small emergency brake shoes can be inspected however the rear calipers and rotors must be removed first. If the emergency brakes still hold then they are probably ok.


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