1990 Chevrolet S10 Pickup Brake Service (ONLINE REPAIR MANUALS)

Refer to Fig. , when replacing power brake unit.

• Disconnect battery ground cable.
• Remove master cylinder as follows:
• Remove air cleaner assembly, then the reservoir lead wire and pressure limit valve wire at electrical connectors.
• Remove fluid from reservoir using a syringe.
• Disconnect and plug three brake fluid lines from master cylinder assembly.
• Remove heat protector bolt from master cylinder bracket.
• Remove two master cylinder ...

DELCO MORAINE TYPE

COMPOSITE TYPE

Refer to Figs. and when performing the following procedures.

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 proportioner 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 remove primary and secondary pistons.
• R...

When working on or around brake assemblies, care must be taken to prevent breathing asbestos dust, as many manufacturers incorporate asbestos fibers in the production of brake linings. During routine service operations, the amount of asbestos dust from brake lining wear is at a low level due to a chemical breakdown during use, and a few precautions will minimize exposure. Do not sand or grind brake linings unless suitable local exhaust ventilation equipment is used to prevent e...

• Raise and support vehicle.
• Remove wheel, drum and brake shoes.
• Disconnect hydraulic line at wheel cylinder. Do not pull metal line away from cylinder, as this may kink or bend line. Line will separate from cylinder when cylinder is moved away from brake backing plate.
• Remove wheel cylinder-to-brake plate attaching screws, then the wheel cylinder.
• Remove boots, pistons, springs and cups from cylinder, Fig. .
• Clean all parts with brake fluid.
• Inspect cylinder bore. A scored bore may be honed as long as the diameter is not increased by ...

Diagnose power brakes systems as if two separate systems exist. Check for faults in the regular brake system first. If no problem exists in the regular brake system, diagnosis the power brake circuit is necessary. For a quick check of proper power unit operation, press the brake pedal firmly and then start the engine. The pedal should fall away slightly and less pressure should be needed to maintain the pedal in any position. On vacuum suspended power units, air will rush into the air intake when the brakes are applied.

To perform another check, remove the stop light switch, ...

WIRING DIAGRAMS

Refer to "Wiring Diagrams" in "Vehicle Systems."

DIAGNOSTIC CIRCUIT CHECK

Refer to Figs. and for diagnostic circuit checks.

READING CODES

Trouble codes may be read with the TECH 1 scanner or by jumping terminal "H " of the ALDL to terminal "A" of the ALDL while observing the flashing of the "Anti-Lock" warning lamp. The terminals must be jumped for a few seconds before the code will begin.""

DIAGNOSTIC TESTS

CLEARING CODES

If the "Anti-Lock" warning lamp stays lit, the codes may be cleared with the TECH 1 scanner or by the following procedu...