2007 GMC Yukon Brake Service (ONLINE REPAIR MANUALS)

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 ...

Master Cylinder

Some vehicles use a conventional tandem master cylinder with two hydraulic pistons operating in-line. The primary piston controls the front brake system and the secondary piston controls the rear brake system.

Other models use a master cylinder that operates the same as the conventional master cylinder, but also incorporates a quick take-up feature in the rear chamber to reduce excessive pedal travel which may result from increased fluid displacement required to move the low drag caliper piston out against the rotor.

The quick take-up uses a spring-loaded ball check val...

The caliper mounts in a way that allows the caliper to move laterally inboard as the brake pads wear. The caliper housing is a one piece casting with the inboard side containing the piston bore. The piston seal also acts as a return mechanism for the piston.

Applying the brake pedal causes the hydraulic pressure that moves the caliper piston. The piston then forces the inboard brake pad against the inboard braking surface of the rotor. Increasing the force against...

Hard Pedal

• Internal vacuum leak.
• Faulty control valve.
• Broken or damaged hydraulic brake lines.
• Collapsed or damaged vacuum hose.
• Plugged or loose vacuum fitting.
• Bad stud welds on front or rear housing on power head.
• Faulty booster diaphragm.
• Restricted air filter element.
• Worn or distorted reaction plate or levers.
• Cracked or broken pow...

Removal

• Siphon ^2/3 of the brake fluid from master cylinder.
• Raise and support vehicle.
• Remove tire and wheel assembly.
• Compress caliper pistons until they bottom in bores using suitable clamp, Fig. .
• Disconnect brake hose at caliper by removing inlet fitting bolt.
• Remove mounting bolts and caliper.

Inspection

Should it become required to remove the caliper for installation of new components, clean components in denatured alcohol, wipe dry using lint-free cloths. Blow out drilled passages and holes using compressed air. Inspect dust boots for punctures or tears. If punctures or tears are...

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...