INTRODUCTION
GENERAL
This section has a description and the service procedures for the brake system. The parts of the brake system include the brake shoes, the wheel cylinders and the parking brake system. A troubleshooting section is include the end of this section.
DESCRIPTION AND OPERATION
A service brake assembly is installed at each end of the drive axle. The parts of the brake system are shown in Figures 1 and 2. When the brake pedal is pushed,fluid pressure from the master cylinder causes the pistons in the wheel cylinders to move out. The pistons cause the brake shoes to expand against the drum.
NOTE: BRAKE ASSEMBLY SHOWN IS FOR THE S30–50E, S60ES, AND S40–50F MODELS
The parking brakes uses the service brake shoes. Additional linkage activates the parking brake system when the lever for the parking brake is pushed down. The parts of the parking brake system are shown in Figures 3 and 4. When the pedal for the parking brakes is pushed, the cables cause the cranks to rotate. This
rotation causes the cable guide to pull on the cable that is connected to the levers for the brake shoes. The levers push the brake shoes against the brake drum. The design of the system permits the tension of each cable to be the same during application of the parking brake.
NOTE: SYSTEM SHOWN IS FOR S30–50E, S60ES AND S40–50F MODELS
1.PARKING BRAKE LEVER ASSEMBLY
2.RELEASE LEVER
3.PEDAL
4.SWITCH
5.CABLE
6.PARKING BRAKE LEVERS
7.CRANK
8.CABLE
9.LEVER
10.PIVOT
11.TO RH BRAKE ASSEMBLY
The clearance between the brake shoes and the brake drum is adjusted automatically. The adjuster linkage turns the adjuster wheel to adjust the clearance. The primary shoe and the adjuster links move with the drum during a stop when the lift truck is moving in reverse. The linkage permits the adjuster lever to rotate the
adjuster screw wheel. The adjuster screw wheel can only turn when there is clearance between the lining and the brake drum. The adjuster screw wheel can also be turned manually. A hole in the drum is used to get access to the adjuster screw wheel.
REPAIRS
WARNING
Brake linings contain asbestos or other fibers. Breathing the dust from these linings is a cancer or lung disease hazard. Do not create dust! Do not clean brake parts with compressed air or by brushing. Use vacuum equipment for asbestos or follow the cleaning procedure in this section. When the brake drums are removed, do not create dust.
Do not sand, grind, chisel, hammer or change linings in any way that will create dust. Any changes to linings must be done in a restricted area with special ventilation. Protective clothing and a respirator must be used.
CLEANING PROCEDURES
1. Do not release brake lining dust from the brake linings into the air when the brake drum is removed.
2. Use a solvent approved for cleaning of brake parts to wet the brake lining dust. Follow the instructions and cautions of the manufacturer for the use of the solvent. If a solvent spray is used, spray at a distance so that the dust is not released into the air.
3. When the brake lining dust is wet, clean the parts. Put any rags or towels in a plastic bag or an airtight container while they are still wet. Put a “DANGEROUS FIBERS” warning label on the plastic bag or airtight container.
4. Any cleaning rags that will be washed must be cleaned so that fibers are not released into the air.
REMOVAL AND DISASSEMBLY
1. Loosen the nuts (inner) that hold the wheel and the drum to the spindle assembly.
2. Start the engine and tilt the mast fully backward. Put blocks under the outer mast channels. Tilt the mast forward on the truck frame.
3. Put some grease on the floor under the wheel. Tilt the mast backward until the wheels just touch the floor.
1.ADJUSTER WHEEL
2.ADJUSTER SCREW NUT
3.PARKING BRAKE LEVER
4.REAR BRAKE SHOE
5.RETURN SPRING
6.WHEEL CYLINDER
7.AUTOMATIC ADJUSTER MECHANISM
8.FRONT BRAKE SHOE
9.PARKING BRAKE LEVER
4. Remove the nuts (inner) that hold the wheel and the drum to the spindle assembly. Remove the wheel and the drum assembly. If necessary, turn the adjuster wheel to
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loosen the brake shoes. Use the hole in the drive wheel to get access to the adjuster wheel.
5. Use spring pliers to remove the return springs for the brake shoes.
CAUTION
The springs are not the same. Make sure the springs are installed to the same positions as during removal.
6. Remove the spring assemblies that hold the brake shoes to the back plate. Remove the brake shoes. Inspect the brake shoes for cracks or damage. If the linings are badly worn or damaged or the shoes are damaged, replace the brake shoes. It is recommended that if one brake shoe is replaced, both shoes on that wheel be replaced.
7. Remove the snap rings that hold the parking brake levers to the back plate. Remove both of the levers and the cable assemblies.
8. Remove the brake lines from the wheel cylinder. Remove the wheel cylinder from the back plate.
9. Remove the boots, the piston, the cups and the springs from the wheel cylinder.
10. Remove the parking brake assembly as described in THE BRAKE SYSTEM, 1800 SRM 87.
11. Remove the back plate.
INSPECTION
1. Check the bore of the wheel cylinder for wear, damage, and holes caused by corrosion. Replace a damaged wheel cylinder.
2. Check the return springs for damaged. Inspect the back plate for wear where the brake shoes touch the back plate. Grind the back plate if it is not smooth.
3. Replace the brake shoes if they are cracked, damaged, or have more than 50% wear. If one brake shoe is replaced both shoes on that wheel must be replaced.
4. Inspect the brake drum for deep grooves or other damage. Use sandpaper on the surface for the brake shoes.
NOTE: If the brake drums require grinding do not grind more than 1.5 mm (0.060 in) from the inner diameter of the brake drum. The maximum drum diameter including wear is 263 mm (10.35 in) S30–60E/F and 320 mm (12.6 in) S60–120E. If the inner diameter is greater than the maximum limit, replace the drum.
5. The teeth of the adjuster wheel must not be worn. The adjuster wheel must turn freely. Check the adjuster links for damage.
6. Make sure the parking brake levers move freely.
7. Check the surfaces of the seals for wear or damage.
ASSEMBLY (See Figures 6, 7, 8)
1. Use clean brake fluid during the assembly of the wheel cylinder. Assemble the wheel cylinder as shown in Figure 6.
2. Install the back plate to the hub. Tighten the four regular capscrews to a torque of 175 N.m (130 lbf ft). Tighten the two special capscrews to a torque of 80 lbf ft (108 N.m) for S30–60E and S40–50F models. For the S60–120E models, tighten the two special capscrews to 150 N.m (110 foot pounds).
3. Install the wheel cylinder and the brake lines.
FIGURE 9. TIGHTENING SEQUENCE
4. Install the actuator levers for the parking brakes. Install the cable and the linkage.
5. Install the brake shoes. Install the spring assemblies that hold the brake shoes to the back plate.
6. Lubricate the adjuster screw with Never–Seeze. Turn the adjuster screw in for installation of the drum.
7. Install the automatic adjuster linkage. Install the return springs for the brake shoes.
8. Put some grease on the floor under the brake assembly. Slide the wheel and drum assembly on the spindle. During installation, start the engine and tilt the mast as necessary to raise or lower the axle.
9. Install the tapered thimbles, the washers and the nuts. Tighten the nuts evenly to 122 N.m (90 lbf ft) in the sequence shown in Figure 9. Tighten the nuts that hold the brake drum to the wheel to a torque of 160 N.m (120 lbf ft) for the S30–60E and S40–50F models. Tighten the nuts to a torque of 270 N.m (200 lbf ft) for the S60–120E models. Tighten the nuts in the sequence shown in Figure 9.
10. Remove the air from the brake fluid as described in Checks and Adjustments in this section.
K. Adjust the service brakes and the parking brakes as described in the Checks and Adjustments in this section.
CHECKS AND ADJUSTMENTS
ADJUSTING THE SERVICE BRAKES
The brake shoes are adjusted automatically in normal operation by applying the service brakes while moving in reverse. To manually adjust the brakes after replacing the shoes or other repair work, put a small screw driver through the hole in the wheel. Push the adjuster spring lever away from the adjuster wheel. Use a brake adjuster tool to turn the star wheel until the brake shoes contact the drum, then back off the star wheel 39 clicks. Move the truck forward and reverse and apply the brakes until the pedal assumes a normal position and becomes stabilized.
ADJUSTING THE PARKING BRAKE
Make sure that the service brakes are adjusted and that the operation of the automatic adjuster mechanism is correct. Test the operation of the parking brake. The lift truck with a capacity load must not move when the parking brake is applied on a 15% grade. If necessary,
the tension of the cable for the parking brake lever can be adjusted. Loosen the lock nut (3) and then turn the adjustment screw (4) to adjust the cable. See Figure 10.
REMOVING THE AIR FROM THE BRAKE SYSTEM
The air must be removed from the brake system. Fill the reservoir of the master cylinder with brake fluid. Put one end of a rubber hose on the special fitting of the wheel cylinder. Put the other end of the hose into a clear container of brake fluid. Loosen the special fitting one turn. Slowly push the brake pedal and hold it at the end of its stroke. Close the special fitting. Repeat the procedure until there are no bubbles in the container. Check the level of the brake fluid in the master cylinder during the procedure. Make sure to keep the brake fluid at the correct level. Repeat the procedure for the other wheel cylinder.
NOTE: On trucks that have a powershift transmission, remove the air from the line for the inching valve. Do the same procedure as described in Removing the Air from the Brake System. The special fitting for removing the air from the system is on the side of the inching valve.
ADJUSTING THE SERVICE BRAKE PEDAL (See Figure 11)
Adjust the height of the brake pedal. Loosen the locknut (1) and turn the adjustment nut (2) to adjust the height of the pedal. For models that have a powershift transmission, adjust the height so that dimensions ”A” is 108 mm (4.25 in). For models that have an oil clutch transmission, adjust the height so that dimension ”A” is 76 mm (3 in).
Adjust the stroke of the push rod to get free movement of the pedal. Loosen the locknut (3) and turn the adjustment nut (4) to adjust the stroke. Adjust the stroke of the push rod so that the free movement of the pedal (dimension ”B”) is 6 mm (0.25 in).