Condition # 1

Owners of some 1988-91 "W" cars equipped with ABS may experience a brake pedal return condition. The stop lamps may also stay illuminated in conjunction with this concern.

Diagnostics:

A. Check brake pedal free back travel when pulling back lightly on pedal (no more than 20 lbs. force).

B. Check stop lamp switch adjustment. Check for stop lamps being illuminated without applying brakes. If stop lamps are not illuminated, measure how far brake pedal travels until stop lamps illuminate.

C. Make a normal brake apply and then a very slow release.

Result:

A. Free back travel is more than 6 mm (1/4 in.).

B. Stop lamps illuminate in less than 10 mm (3/8 in.) of pedal travel or are illuminated constantly

C. Brake pedal does not return to its original position.

Corrective Action:

A. Pull Powermaster III unit away from cowl. If push rod is not attached firmly, replace push rod retainer (P/N 18020694).

B. Adjust stop lamp switch per Service Manual instructions.

C. See corrective action Step # 1 below.



CORRECTIVE ACTION STEPS:

Step # 1 - Brake pedal does not return to its original position.

A. Repair the unit with Powermaster Repair Kit P/N 18017614.

NOTE:





It is critical to follow the Powermaster III overhaul procedure that is included with the kit. Procedure for Powermaster III units with stop pin (Figure 1) is different than procedure for units without stop pin. All 1990 and 1991 vehicles should have the stop pin.

NOTE:
Proper seating of the conduit retainer during POWERMASTER III ASSEMBLY is critical. If the Powermaster III unit does not have a stop pin (Figure 1), proper seating of the conduit retainer cannot be verified until after unit installation on vehicle and test.

NOTE:
When a Powermaster III unit with a stop pin (Figure 1) is depressurized, a hard manual brake apply should be the last step before recharging the system.