Mercedes Coupes/Sedans/Wagons 1974-1984 Repair Guide



See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: The arrow indicates the location of the reset pin on a master cylinder equipped with a pressure differential warning valve

All Mercedes-Benz cars imported into the U.S. are equipped with 4-wheel disc brakes. The disc brakes are basically similar on all models, though there may be slight differences in design from model to model. The caliper bore sizes, for instance, differ depending upon application. The bore size (in mm) is usually stamped on the outside of the caliper, but occasionally, a code is used. For instance, the 14 on a Teves (ATE) caliper is really a 57 mm bore (obviously, it isn't a 14mm bore).

Three different manufacturers make calipers for Mercedes-Benz productionTeves (ATE), Bendix or Girlingbut calipers of the same manufacturer are installed on the same axle. For service, install calipers of the same manufacturer on the front axle; on the rear axle, calipers of any manufacturer can be installed.

Most models are equipped with brake pad wear indicators to indicate when the pad lining requires replacement. Beginning in 1976, a new design, step-type master cylinder is used which eliminates the need for the vacuum pump previously used on 230, 280, 280C and 280S. The brake circuits are reversed from 1974 and 1975 models; the front brakes are connected to the primary side of the master cylinder and the rear brakes to the secondary side. A pressure differential warning indicator is also used, which will immediately indicate the total loss of one part of the braking system by lighting the brake warning light on the dash. Once the warning light has come on, it will remain on until the system is repaired and the switch on the master cylinder reset. The warning light will only go out after pushing the reset pin in the switch.

Beginning with 1978 models, the pressure differential warning indicator has been eliminated from models with the step-type master cylinder. The master cylinder reservoir has 2 chambers with 2 sets of electrical contacts. Loss of brake fluid in either reservoir will light the warning light on the dash.

Since disc brakes are used at all four wheels, no adjustments are necessary. Disc brakes are inherently self-adjusting. The only adjustment possible is to the handbrake, which is covered at the end of this section.