2007 Hummer H3 Brake Service (ONLINE REPAIR MANUALS)

When wheel slip is detected during a brake application, the ABS enters anti-lock mode. During anti-lock braking, hydraulic pressure in the individual wheel circuits is controlled to prevent any wheel from slipping. A separate hydraulic line and specific solenoid valves are provided for each wheel. The ABS can decrease, hold, or increase hydraulic pressure to each wheel brake. The ABS cannot, however, increase hydraulic pressure above the amount which is transmitted by the master cylinder during braking.

During anti-lock braking, a series of rapid pulsations is felt in the brake pedal...

Manual Bleed

• If vehicle is equipped with power brakes, remove vacuum reserve by applying brakes several times with engine off.
• Fill master cylinder reservoirs with suitable brake fluid. Ensure to always keep master cylinder reservoirs at least half full during entire bleeding procedure.
• If master cylinder is suspected to have air in bore, it must be bled first. To bleed master cylinder, proceed as follows:
• Disconnect forward brake pipe connection at master cylinder.
• Allow brake fluid to fill master cylinder bore until it begins to flow from forward pipe connector port.
• Connect and ...

In order to properly service power brake systems, a thorough understanding of the various power assist systems is required. These systems provide a mechanical assist, acting to increase the force applied to the master cylinder piston by the driver while decreasing the effort required 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 (us...

Removal

Front

• Siphon brake fluid out of master cylinder until fluid level is approximately ^1/3 full, this will prevent fluid overflow when caliper piston is pushed back into its bore.
• Raise and support vehicle, then remove wheels.
• Push piston back into its bore using suitable C-clamp, Fig. .
• Remove brake caliper hose bolt, then two metal gaskets from brake caliper bolt.
• Remove two caliper mounting bolts and lift caliper off of rotor.

Rear

• Siphon brake fluid out of master cylinder until fluid level is approximately ^1/3 full, this will prevent fluid overflow when caliper piston is pushed ...

Acadia, Enclave & Outlook

• Apply park brake, then with engine off, apply and release brake pedal several times until brake pedal becomes firm to deplete vacuum reserve in vacuum brake booster.
• Remove air cleaner assembly.
• Disconnect master cylinder fluid level sensor electrical connector.
• Remove vacuum brake booster check valve and hose assembly from vacuum brake booster and position aside.
• Remove vacuum brake booster vacuum sensor and position aside.
• Release front and rear brake pipes from routing clip on frame rail.
• Remove Brake Pressure Modulator Valve (BPMV) assembly mount...

Delco Master Cylinder

When performing the following procedures, refer to Fig. noting that the composite reservoir may vary in design.

Disassemble

• Remove master cylinder from vehicle.
• Remove reservoir cover and diaphragm. Discard old brake fluid in reservoir.
• Inspect cover and diaphragm. Replace if cut, cracked or deformed.
• Remove fluid level switch and proportioning valve assembly, if equipped.
• Depress primary piston and remove lock ring.
• Plug primary fluid outlet (outlet nearest to cowl when master cylinder is installed), then apply compressed air into secondary fluid outlet to remo...