Hydraulic Brake Booster (Hydro-Boost); Description - GMC 1986 P-Truck Service Manual

Tighten
• Mounting nuts to 34 N m (25 ft. lbs.
7. Release the parking brakes.

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
C-K AND G MODELS
+-► Remove or Disconnect (Figure 29)
• Apply the vehicles parking brakes.
1. Hydraulic lines from the booster.
2. Nuts (1).
3. Master cylinder (2).
• Support the master cylinder.
4. B o o ste r p u sh ro d , re fe r to " Brake Pedal
Replacement" in this section.
5. Nuts (4) and (6).
6. Hydro-Boost unit (3).
• Gasket (5).
Install or Connect (Figure 29)
NOTICE: For steps 2 and 5 see "Notice" on
page 5-1 of this section.
1. Gasket (5).
• Hydro-Boost unit (3).
2. Nuts (4) and (6).
Tighten
• Nuts to 34 N m (25 ft. lbs.).
3. B o o ste r p u sh ro d , re fe r to " B rake Pedal
Replacement" in this section.
4. Master cylinder. (2).
5. Nuts (1).
£ Tighten
• Nuts to 34 N m (25 ft. lbs.).
6. Hydraulic lines.
7. Bleed the booster, refer to " B leeding the
Hydro-Boost System" in this section.
8. Release the parking brakes.
P 30 (42) MODEL
Remove or Disconnect (Figure 30 and 31)
• Apply the vehicles parking brakes.
1. Hydraulic lines from the booster.
2. Nuts (1) and washers (7).
3. Master cylinder (2).
• Support the master cylinder.
4. Pushrod retainer (10).
5. Retaining clip and washer.
• Booster pushrod (9).
6. Nuts (4) and washers (8).
7. Hydro-Boost unit (3).
-►+ Install or Connect (Figure 30 and 31)
NOTICE: For steps 2 and 6 see "Notice" on
page 5-1 of this section.
1. Hydro-Boost unit (3).
2. Washers (8) and nuts (4).
• Nuts to 34 N m (25 ft. lbs.).
3. Booster pushrod (9).
• Washer and retaining clip.
4. Pushrod retainer (10).
5. Master cylinder (2).
6. Washers (7) and nuts (1).
Tighten
• Nuts to 34 N m (25 ft. lbs.)
7. Hydraulic lines.
8. Bleed the booster, refer to " Bleeding the
Hydro-Boost System" in this section.
BRAKES 5-33