Description; Hydraulic Brake Booster (Hydro-Boost); Hydro-Boost Replacement - GMC G Service Manual

5A1-4 HYDRAULIC BRAKE BOOSTER SYSTEMS
1. Mounting Nuts
2. Master Cylinder
3. Vacuum Booster
4. Booster Mounting Nuts
5. Booster Pushrod
Figure 2 — Removing/Installing Vacuum Boosters

HYDRAULIC BRAKE BOOSTER (HYDRO-BOOST)

DESCRIPTION

This system uses a hydraulic pump to power the system
and a pneumatic accumulator as a reserve system.
In this system, no special fluids are used, however, care
must be taken to use the correct fluids. The master cylinder
and brake system operate on standard hydraulic brake
fluid, while the hydraulic pump operates on power steering
fluid. For diagnosis of the Hydro-Boost System, refer to
"Hydro-Boost Systems Tests" and "Diagnosis of Hydro-
Boost System" in this section.

HYDRO-BOOST REPLACEMENT

R/V AND G-MODELS
M Remove or Disconnect (Figure 3)
• Apply the parking brake.
1. Hydraulic lines from the booster.
2. Nuts (1).
3. Master cylinder (2).
• Support the master cylinder.
4. Booster pushrod. Refer to HYDRAULIC BRAKES
(SEC. 5A).
5. Nuts (4) and (6).
6. Hydro-Boost unit (3).
7. Gasket (5).
E
Install or Connect (Figure 2)
NOTICE: For steps 2 and 6 see " Notice" on page
5A1-1 of this section.
1. Vacuum booster (3).
2. Booster mounting nuts (4).
Tighten
• Nuts to "Specifications" at the end of this
section.
3. Booster pushrod (5). Refer to HYDRAULIC BRAKES
(SEC. 5A).
4. Vacuum hose.
5. Master cylinder (2).
6. Mounting nuts (1).
B-07805
Tighten
• Mounting nuts to "Specifications" at the end of
this section.
7. Release the parking brakes.
R install or Connect (Figure 3)
NOTICE: For steps 3 and 6 see " Notice" on page
5A1-1 of this section.
1. Gasket (5).
2. Hydro-Boost unit (3).
3. Nuts (4) and (6).
I^ \l Tighten
• Nuts to "Specifications" at the end of this
section.
4. Booster pushrod. Refer to HYDRAULIC BRAKES
(SEC. 5A).
5. Master cylinder (2).
6. Nuts (1).
Tighten
• Nuts to "Specifications" at the end of this
section.
7. Hydraulic lines.
• Bleed the booster. Refer to "Bleeding the Hydro-
Boost System" in this section.