Figure 3-44. Wheel cylinder, exploded view.

c. The seat brake is a fully enclosed, two shoe.

Caution: Do not use mineral base solvents

mechanical brake. Equal pressure is applied to both

such as gasoline, kerosene, carbon tetrachloride,

shoes when the brake is actuated (seat unoccupied).

acetone, point thinners, etc., to clean rubber parts.

The directional control is electronically returned to a

(4) Clean wheel cylinder internal parts using a

"Neutral" condition when the seat brake is actuated.

lint-free cloth dampened in clean denatured alcohol or

hydraulic brake fluid.

3-31. Hydraulic Wheel Cylinder

(5) Inspect parts for corrosion.

(6) Inspect piston surfaces for scratching or

a. Removal. Remove the wheel cylinder (Tm 10-

pitting.

3930-620-12).

(7) Inspect rubber parts for deterioration,

b. Disassembly. Cleaning. and Inspection. (fig. 3-

swelling, softening, tackiness, and lack of springaction.

44.)

(8) Replace all parts which appear to be worn or

(1)Remove rubber boots (1) from openings at end

damaged.

of wheel cylinder.

(9) Inspect cylinder bore for deep blemishes,

(2) Remove pistons (2), piston caps (3), and spring

scratching, or pitting.

(4) from wheel cylinder.

(10) If scratching, pitting, or deep blemishes are

(3) Low pressure air may be used to remove

found in cylinder bore, remove cylinder and recondition in

internal parts of wheel cylinder by applying air pressure

accordance with subparagraph c.

at hydraulic brake fluid inlet, if required.

1. Boot (2)

4. Spring

2. Piston (2)

5. Bleeder screw

3. Piston (2)

6. Cylinder

Figure 3-44. Wheel cylinder, exploded view.

c. Repair.

(7) Clean cylinder body using clean, soapy

(1) Insure that wheel cylinder has been cleaned in

water.

accordance with subparagraph b.

(8) Rinse cylinder body using clean, warm water.

(2) Apply a coating of clean hydraulic brake fluid

Warning: Wear suitable eye protection when

to walls of cylinder bore.

using compressed air.

Caution: Do not distort or crack cylinder body when

(9)

Dry cylinder body using compressed air.

securing cylinder in vise.

d. Reassembly. (fig. 3-44.)

(3) Secure wheel cylinder in vise.

Note. If cylinder bore has been honed, insure

Note. Before honing cylinder bore, become

that new parts contained in repair kit are installed.

familiar with honing equipment manufacturer's

(1) Apply a coating of clean hydraulic brake fluid

operating and servicing instructions.

to walls of cylinder bore and all internal wheel cylinder

(4) Using honing equipment, remove scratching,

parts.

pitting, etc. from cylinder bore in single passes.

Note. Do not push pistons through full

(5) After each pass is completed, visually check

length of cylinder bore.

cylinder bore for the absence of scratching, pitting, etc.

(2) Install spring (4), piston caps (3), and pistons

(6) If scratching, pitting, etc., is deep or

(2) into wheel cylinder.

excessive and wheel cylinder bore would have to be

(3) Install rubber boots I1 on openings at end of

honed oversize (greater than 1.5070 inches), replace

wheel cylinder.

cylinder.

3-64