1996 GMC K3500 Pickup Brake Service (ONLINE REPAIR MANUALS)

In order to properly service power brake systems, a thorough understanding of the various power assist systems is necessary. These systems provide a mechanical assist, acting to increase the force applied to the master cylinder piston by the driver while decreasing the effort necessary to obtain acceptable stopping performance. Two basic types of power assist mechanisms are used: vacuum assist diaphragm assemblies which use engine vacuum and in some cases vacuum from an external vacuum pump, and hydraulic assist assemblies which use hydraulic pressure developed by an external pump (...

Height Sensing Proportioning Valve

The height sensing proportioning valve must be adjusted whenever the valve and/or linkage is disassembled or removed for service. In addition, adjustment should be checked if excessive front wheel lock-up is experienced with a lower than desired brake application rate when vehicle is at or near maximum GVWR.

• Raise and support vehicle leaving wheels on, and allow axle to hang freely.
• Remove lever retaining nut and disconnect lever from valve shaft, Fig. .
• Rotate valve shaft to permit installation of correct adjustment gauge, Fig. , ensuring that D shape...

Disassemble

• Place accumulator compressor tool No. J-26889 or equivalent, around end of accumulator.
• Install nut onto stud as shown in Fig. , then depress the accumulator with a C-clamp.
• Remove retainer by using a punch.
• Release C-clamp and remove accumulator compressor tool.
• Remove accumulator, O-ring, retainer, plug and spring, Fig. .
• Remove retainer, output pushrod, baffle, piston return spring and retainer.
• Using a suitable saw, cut off eyelet of pedal rod, then remove the boot.
• Remove nut, bracket and bolts, then separate cover from housing.
• Remove piston assembly and seals...

Single Diaphragm Type

Disassemble

• Remove boot, silencer, vacuum check valve, grommet and front housing seal, Fig. .
• Scribe a line across front and rear housing, then mount brake booster to brake mounting fixture tool No. J 23456 or equivalent, Fig. .
• Turn fixture handle counterclockwise to unlock housings.
• Remove return spring, power piston assembly and power piston bearing from rear housing, Fig. .
• Remove reaction body retainer, piston rod, reaction retainer and filter.
• Remove power piston and pushrod assembly as follows:
• While holding the pushrod down against a hard surface, ...

Master Cylinder

• On models with manual brake system, disconnect master cylinder pushrod from brake pedal.
• On all models, disconnect all wire connector...

When troubleshooting the anti-lock brake system, refer to "Wiring Diagrams" in "Vehicle Systems" and connectors, Figs. through ; these may be helpful in completing a visual inspection of all relat...