Brake System Bleeding GMC Vandura I

DESCRIPTION

Note. For model specific brake bleeding procedures, see appropriate BRAKE SYSTEM article in the BRAKES Section.

Hydraulic system bleeding is necessary any time air has been introduced into system. Bleed brakes at all 4 wheels if master cylinder lines have been disconnected or master cylinder has been run dry. Bleed brakes with pressure bleeding equipment or by manually pumping brake pedal while using bleeder tubes.

HYDRAULIC CONTROL VALVES

On disc brake equipped vehicles, metering section of hydraulic control valve must be deactivated before bleeding to permit fluid to flow to front brakes. This is especially important when pressure bleeding.

Use pressure tool when applicable (J-23709, General Motors) If tool is not available, hold valve open by hand. DO NOT use "C" clamp or other non-yielding device to hold valve open.

PRESSURE TANK BLEEDING

1. Clean master cylinder cap and surrounding area. Remove cap. With pressure tank at least 1/2 full, connect to master cylinder with adapters. Attach bleeder hose to first bleeder valve to be serviced. See Bleeding Sequence table.
2. Place other end of hose in clean glass jar partially filled with clean brake fluid so end of hose is submerged in fluid. Open release valve on pressure bleeder. Follow equipment manufacturers pressure instructions unless noted below.
3. Unscrew bleeder valve 3/4-1 turn noting fluid flow. When fluid flowing from cylinder to jar is free of bubbles, close bleeder valve securely. Bleed remaining cylinders in correct sequence and in the same manner. Remove tool from control valve.

PRESSURE BLEEDER SETTINGS

MANUAL BLEEDING

Note. When bleeding disc brakes, air may tend to cling to caliper walls. Lightly tap caliper, while bleeding, to aid in removal of air.

1. Fill master cylinder. Install bleeder hose to first bleeder valve to be serviced. See Bleeding Sequence table. Submerge other end of hose in clean glass jar partially filled with clean brake fluid.
2. Open bleeder valve 3/4-1 turn. Depress brake pedal slowly through full travel. Close bleeder valve and release pedal. Repeat procedure until flow of fluid shows no signs of air bubbles.

Wheel Cylinder Bleeding Procedure Bleeder valve must be closed when brake pedal is released. Scheme 1

BLEEDING SEQUENCE

Before bleeding system, exhaust all vacuum from power unit by depressing brake pedal several times. Bleed master cylinder if equipped with bleeder screws. Bleed slave cylinder on vehicles equipped with remote mount power assist units. Bleed wheel cylinders and calipers in sequence. See Bleeding Sequence table.

BLEEDING SEQUENCE

See also:
• BRAKE SYSTEM