Chevrolet Cobalt Service & Repair Manual: Component Service

Chevrolet Cobalt Service & Repair Manual / Brakes / Hydraulic Brake Systems / Component Service

Master Cylinder Overhaul

Impala

Disassemble
Refer to Figs. 1 and 2, when performing the following procedures.
1. Disconnect and plug hydraulic lines.
2. Remove mounting nuts and master cylinder.
3. Remove reservoir cover and diaphragm. Discard old brake fluid.
4. Inspect cover and diaphragm.
5. Remove fluid level switch.
6. On models equipped with compact master cylinder,remove proportioning valve, Fig. 2.
7. On all models, depress primary piston and remove lock ring.
8. Plug primary fluid outlet (outlet nearest to cowl when master cylinder is installed), then remove primary and secondary pistons by applying compressed air into secondary fluid outlet.
9. Remove secondary piston spring retainer and seals.
10. Remove secondary piston spring retainer and seals.
11. Clamp the flange on the master cylinder body in a vise, then remove fluid reservoir, Figs. 3 and 4.
12. Remove reservoir grommets.
13. Inspect master cylinder bore for corrosion. Do not use abrasive material on master cylinder bore.
Assemble
Clean all components not included in repair kit with suitable brake fluid. Do not dry with compressed air. Lubricate all rubber components with clean brake fluid prior to installation.
1. Lubricate new reservoir grommets with suitable silicone brake lube.
2. Press grommets into master cylinder body. Ensure grommets are properly seated.
3. Lay reservoir upside down on flat, hard surface.
4. Press master cylinder body onto reservoir using rocking motion.
5. Install new seals on secondary piston and spring retainer.
6. Install spring and secondary piston into cylinder.
7. Install primary piston.
8. Depress primary piston into cylinder and install lock ring.
9. Install fluid level switch, if equipped.
10. On models equipped with compact master cylinder,install proportioning valve, Fig. 2.
11. On all models, install diaphragm into reservoir cover and cover onto reservoir.
12. Install master cylinder and bleed brake system.

Cobalt, DTS, G6, Lucerne, Malibu & SKY

These master cylinders are not serviceable. Master cylinder must be replaced as a complete unit. Do not attempt to overhaul the master cylinder.

Aveo & G3

1. Disconnect electrical connector from reservoir.
2. Disconnect brake lines from master cylinder.
3. Plug brake line openings to prevent fluid loss and contamination.
4. Remove power booster mounting nuts.
5. Remove master cylinder assembly.
6. Remove brake fluid reservoir.
7. Remove seal ring from cylinder bore.
8. Remove retaining ring from cylinder body using suitable flat bladed tool. Discard ring.
9. Remove primary piston.
10. Carefully remove secondary piston assembly and spring from master cylinder bore.
11. Reverse procedure to install, noting the following:
  a. Clean all parts with clean brake fluid, then dry with compressed air.
  b. Replace all rubber parts and retaining rings.
  c. Lubricate master cylinder bore with clean brake fluid.

Corvette

1. Remove reservoir cap and diaphragm.
2. Drain fluid into suitable container.
3. Remove master cylinder prime pipe clamp and prime pipe.
4. Remove mounting screw and reservoir, Fig. 5.
5. Remove reservoir O-rings.
6. Slightly depress piston and remove retaining ring using suitable retaining ring pliers.
7. Invert cylinder so reservoir wells face downward.
8. Depress primary and secondary pistons until fully bottomed in bore using suitable brass rod or wooden dowel. Secondary stop pin should fall freely from cylinder.
9. Gently bump open end of cylinder body against suitable wood piece to dislodge primary piston. Remove primary piston.
10. Gently bump open end of cylinder body against suitable wood piece to dislodge secondary piston and center valve. Remove secondary piston. Do not remove or disturb screw which retains primary spring to secondary piston.
11. Remove secondary return spring.
12. Remove secondary piston spring retainer using suitable small screwdriver to lift crimp and allow retainer to slide off piston, Fig. 6.
13. Remove secondary piston center valve plunger and spring.
14. Remove primary piston seal retainer using suitable sharp knife or razor blade to cut and remove plastic retaining cup retaining ring, Fig. 7.
15. Remove recuperating guide.
16. Remove pistons' rubber seals, Figs. 8 and 9. Do not damage any piston surfaces, particularly areas where seals seat.
17. Remove pressure differential switch. Do not disassemble spring or probe.
18. Remove end plug and O-ring. Do not lose small electrical bias spring located just inside end plug.
19. Remove warning switch. Keep warning switch and probe together as an assembly.
20. Remove end plug, O-ring and electrical bias spring.
21. Gently tap cylinder body against suitable wood piece to dislodge proportioning valve spool.
22. Remove proportioning valve spool including O-ring and spacer. Do not disassemble proportioning valve.
23. Proportioning valve is lubricated with special grease. Do not use cleaning solution to clean it or components included in repair kit. Clean other components in suitable denatured alcohol. Dry components and passages within cylinder using filtered compressed air.
24. Reverse procedure to assemble. Ensure seals and components are lubricated with clean brake fluid.

CTS

1. Remove master cylinder as outlined in Component Replacement.
2. Place mounting flange into suitable vise so piston is accessible.
3. Ensure outside area of master cylinder is clean of dirt and debris.
4. Remove reservoir cap and diaphragm.
5. Remove fluid level sensor and drain master cylinder reservoir brake fluid into suitable container.
6. Remove retaining pins and reservoir from master cylinder.
7. Remove seals from master cylinder reservoir.
8. Remove piston retainer using suitable tool.
9. Remove piston from cylinder bore.
10. Plug cylinder inlet ports and rear outlet port, then apply low pressure compressed air into front outlet port to remove secondary piston assembly.
11. Reverse procedure to install.

LaCrosse & STS

Disassemble
1. Remove master cylinder as outlined in Component Replacement.
2. Secure master cylinder mounting flange in suitable bench vise so primary piston rear is accessible.
3. Clean outside of master cylinder reservoir, then remove reservoir cap and diaphragm.
4. Replace cap and diaphragm if cut or cracked, nicked or deformed.
5. Secure master cylinder in suitable vise. Do not clamp master cylinder body, secure only at flange.
6. Remove brake fluid level sensor by depressing tab with suitable nose pliers and pressing sensor through reservoir.
7. Tap out reservoir retaining pins.
8. Remove reservoir and seals.
9. Depress primary piston using smooth, round-ended tool and remove piston retainer.
10. Remove primary piston from cylinder bore.
11. Plug cylinder inlet and rear outlet ports.
12. Apply low pressure, non-lubricated, filtered air into front outlet port and remove secondary piston with primary and secondary seals, and return spring.
13. Discard primary piston assembly, piston retainer, seals and retainer from secondary piston.
Assemble
1. Clean interior and exterior of master cylinder, secondary piston and return spring in denatured alcohol, or equivalent.
2. Inspect the master cylinder bore, inlet and outlet ports, secondary piston and return spring for cracks, scoring, pitting, and/or corrosion.
3. Dry master cylinder and components with non-lubricated, filtered air.
4. Lubricate master cylinder bore, secondary piston, return spring and components with suitable brake fluid.
5. Assemble lubricated, new primary seal, retainer and new secondary seal onto secondary piston.
6. Install lubricated return spring and secondary piston assembly into cylinder bore.
7. Install lubricated, new primary piston assembly into cylinder bore.
8. Depress primary piston using smooth, round-ended tool, and install new piston retainer.
9. Install lubricated reservoir seals. Ensure they are fully seated.
10. Install reservoir by pressing reservoir straight down on master cylinder until pin holes are aligned.
11. Tap reservoir retaining pins into place.
12. Place brake fluid level sensor into reservoir and press into place.
13. Install reservoir cap and diaphragm.

Vibe

1. Remove master cylinder from vehicle as outlined in Component Replacement.
2. Remove master cylinder bore O-ring and two attaching rubber grommets.
3. Secure master cylinder into suitable vise, then remove piston stopper bolt and gasket.
4. Remove snap ring pushing piston into master cylinder.
5. Remove plate, cylinder cup, O-ring, piston guide and primary piston assembly from master cylinder.
6. Remove secondary piston using suitable hammer to tap cylinder flange against blocks.
7. Inspect components for wear and damage, replace as required.
8. Reverse procedure to install. Bleed brake system as outlined in Brake System Bleed.

Wheel Cylinder Overhaul

Disassemble

1. Raise and support vehicle.
2. Remove wheel, drum and brake shoes.
3. Disconnect hydraulic line at wheel cylinder. Do not pull metal line away from cylinder. Line will separate from cylinder when cylinder is moved away from brake backing plate.
4. Remove mounting screws and wheel cylinder.
5. Remove boots, pistons, springs and cups, Fig. 10.

Assemble

1. Clean components with suitable brake fluid.
2. Inspect cylinder bore. Scored bore may be honed as long as diameter is not increased by more than .005 inch.
3. Ensure hands are clean before proceeding.
4. Lubricate cylinder wall and rubber cups with suitable brake fluid.
5. Install springs, cups, pistons and boots.
6. Wipe end of hydraulic line to remove any foreign matter and place wheel cylinder in position.
7. Enter tubing into cylinder and start threads on fitting.
8. Secure cylinder to backing plate and complete tightening of tubing fitting.
9. Install brake shoes, drum and wheel.
10. Bleed brake system and adjust brakes.

Fig. 1 Dual master cylinder assembly. Impala

Fig. 2 Compact master cylinder assembly. Impala

Fig. 3 Master cylinder reservoir replacement. Composite type less retaining pins

Fig. 4 Master cylinder reservoir replacement. Composite type w/retaining pins

Fig. 5 Composite master cylinder replacement. Corvette

Fig. 6 Lifting crimp on secondary spring retainer replacement. Corvette

Fig. 7 Seal retainer cutting. Corvette

Fig. 8 Primary piston components. Corvette

Fig. 9 Secondary piston components. Corvette

Fig. 10 Exploded view of wheel cylinder

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