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Home >> GMC >> 1990 >> Forward Control 7.4 N, Automatic, 400/M40 >> Repair and Diagnosis >> Brakes >> Mechanical - Hydraulic >> DISC & DRUM (C, G, K, P, R & V Series) >> Bleeding >> Hydraulic Control Valves

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 Combination Valve Depressor (J-23709 or J-25856) when applicable. See Fig 1. If tool is not available, hold valve open by hand. DO NOT  use "C" clamp or other non-yielding device to hold valve open.

Fig 1: Positioning Combination Valve Depressor
G117380Courtesy of GENERAL MOTORS CORP.