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The piston boots are of the press-on type and prevent moisture from entering the wheel cylinder.
To perform service operations or inspections of the wheel cylinders, it will be necessary to remove the cylinders from the support plate and disassemble on the bench.
Caution: Wheel cylinders with cup expanders must have cup expanders after any service procedures (reconditioning or replacement).
With brake drums removed, inspect the wheel cylinder boots for evidence of a brake fluid leak. Block brake pedal in stroke position, visually check the boots for cuts, tears, or heat cracks, and if any of these conditions exist, the wheel cylinders should be completely cleaned, inspected and new parts installed (Fig.
1). (A slight amount of fluid on the boot may not be a leak, but may be preservative fluid used at assembly.)
(1) In case of a leak, remove brake shoes, (replace if soaked with grease or brake fluid.)
(2) Disconnect brake tube from wheel cylinder.
(3) Remove wheel cylinder attaching bolts, then pull wheel cylinder assembly out of support.
To disassemble the wheel cylinders, (Fig. 2) proceed as follows:
(1) Using a suitable tool, pry boots away from cylinders and remove. Remove push rods.
(2) Press in on one piston and force out piston, cups, spring (with cup expanders), cup and piston.
(3) Wash wheel cylinder, pistons, and spring in clean brake fluid or alcohol; clean thoroughly and blow dry with compressed air. Inspect cylinder bore and piston for scoring and pitting. (Do not use a rag as lint from the rag will adhere to bore surfaces.)
Wheel cylinder bores and pistons that are badly scored or pitted should be replaced. Cylinder walls that have light scratches, or show signs of corrosion, can usually be cleaned with crocus cloth, using a circular motion. Black stains on the cylinder walls are caused by piston cups and will not impair operation of cylinder.
Before assembling the pistons and new cups in the wheel cylinders, dip them in clean brake fluid. If the boots are deteriorated, cracked or do not fit tightly on the push rods or the cylinder casting, install new boots.
(1) Coat cylinder bore with clean brake fluid.
(2) Install expansion spring with cup expanders in cylinder. Install cups in each end of cylinder with open end of cups facing each other.
(3) Install piston in each end of cylinder having the flat face of each piston contacting the flat face of each cup, already installed.
(4) Install a boot over each end of cylinder and press over ends until boot is seated against cylinder shoulder. Use care not to damage boot.
(5) Lubricate spherical end of each push rod with brake fluid and insert each into boot.
(1) Apply RTV sealant around wheel cylinder mounting surface.
(2) Slide wheel cylinder into position on support. Install mounting screws and tighten as specified.
(3) Connect brake tube to wheel cylinder.