Thursday, July 11, 2013

Colt 1974-75 Brake Repair Guide

Brake system is hydraulically actuated, using a tandem master cylinder and on models equipped with the 2000cc engine, a power brake unit. All models are equipped with disc brakes on the front wheels and drum brakes on the rear wheels. Front disc brakes consist of a rotor and a single piston, floating caliper assembly. Rear brakes are self-adjusting, leading-trailing shoe/drum type, actuated by a dual piston wheel cylinder. Parking brake is cable actuated, operating on the rear wheel brake assemblies.

Front disc brakes are self-adjusting, therefore, no adjustment in service is required.
Rear drum brakes are self-adjusting, therefore, no adjustment is necessary.
Adjust pedal height (distance from top of brake pedal to toe board) to specifications by moving pedal stopper (stop light switch). Pedal height should be 6.9-7.1" (175-180 mm) for models without power brakes and 6.5-6.7" (165-170 mm) for models equipped with power brakes. After pedal height is adjusted, loosen push rod lock nut and adjust pedal free play to .5-.6" (10-15 mm).
1) Release parking brake lever. Loosen cable attaching bolt and adjusting nut, and move cable lever to right. Adjust clearance of left to .04" (1.0 mm), then tighten attaching bolt. Clearance is measured between extension lever and stopper.
2) With left cable adjusted, turn adjusting nut until some clearance is obtained on right extension lever. With

parking brake properly adjusted, lever stroke should be 4-6 inches (8-12 clicks).
Attach a bleed tube to wheel cylinder bleeder screw and immerse opposite end of tube in a container partially filled with brake fluid. Depress and release pedal several times, hold in applied position, loosen bleeder screw, allow air to escape and tighten bleeder screw. Continue operation until air bubbles are no longer seen in discharged fluid. Repeat procedure at remaining brake lines until all air is bled from system. Bleeding sequence is right-rear, left-rear, left-front, and right-front.
Removal - Raise and support vehicle and remove front wheel. Remove pad protector by prying up edge of clip at center of protector. Hold center of "M" clip, detach "M" clip from pad and its ends from retaining pins, remove lip. Remove retaining pins from caliper and remove "K" spring. Remove pads from caliper by graspiug backing plate are of pads with pliers.
Installation - Press piston to bottom of bore using a suitable tool, install disc pads and retaining pins. Install "K" spring and "M" clip, making sure positions are not reversed. See illustration. Install pad protector, making sure clips force outward.
Removal - With disc pads, removed, disconnect hydraulic line and remove bolts attaching caliper assembly to steering knuckle, and remove caliper assembly.
Installation - Reverse removal procedure, tighten caliper mounting bolts evenly, and bleed hydraulic system.
Removal - With caliper assembly removed, remove hub dust, cap, cotter pin, lock nut, and adjustment nut. Pull hub and rotor assembly from spindle, taking care not to drop outer wheel bearing. Remove bolts attaching rotor to hub, then separate.
Installation - Reverse removal procedure, tighten rotor-to-hub bolts evenly, and adjust wheel bearings.

Removal - Raise and support vehicle and remove brake drum. Remove shoe hold-down springs. Disconnect strut-to-shoe spring and upper shoe return spring end from trailing shoe. Remove trailing shoe and lower return spring. Hold adjusting latch downward, pull adjusting lever toward center of brake, and remove leading shoe assembly. Remove upper shoe return spring and strut-to-shoe spring.
Installation - Reverse removal procedure and note the following: Apply brake grease to all shoe contact points of backing plate, adjuster assembly, and wheel cylinder. Adjust amount of engagement of adjusting lever with strut only after amount of engagement of adjusting lever with strut only after pulling lever fully toward center of brake. Note that adjusting lever and latch spring differ between right and left sides.
Removal - With rear drum and brake shoes removed, disconnect hydraulic line from wheel cylinder at rear of backing plate, remove bolts attaching cylinder, and remove wheel cylinder.
Installation - Reverse removal procedure, tighten mounting bolts evenly, and bleed hydraulic system.
Removal - Disconnect hydraulic lines from master cylinder, then depress brake pedal slowly several times to discharge brake fluid. On models with power brakes, remove clevis bolt retaining master cylinder push rod to brake pedal, then on all models, remove cylinder attaching bolts and lift off master cylinder.
Installation - Reverse removal procedure, check and adjust pedal height, and bleed hydraulic system.
Removal - With master cylinder removed, disconnect vacuum hose from power brake unit. Remove pin connecting power unit operating rod to brake pedal, then loosen attaching nuts and remove power unit.
Installation - Reverse removal procedure and note the following: Apply a suitable sealer to power unit mounting surface and vacuum line connections. Adjust pedal height and bleed hydraulic system.

Disassembly - Remove caliper attaching bridge bolts and separate outer and inner halves. Remove retaining ring and dust seal, apply compressed air to fluid inlet, and remove piston. Remove piston seal taking care not to damage caliper bore or seal groove.
Cleaning & Inspection - Clean all metal parts in trichloroethlene, alcohol, or brake fluid; clean piston seal in brake fluid or alcohol; clean dust seal and other rubber parts in alcohol only. Inspect caliper bore and piston for wear, damage, or rust; replace parts as necessary.
NOTE - Manufacturer recommends replacing piston seal and dust seal whenever piston has been removed.
Reassembly - Reverse disassembly procedure and note the following: Apply rubber grease to piston seal and brake fluid to piston when reassembling. If torque plate was removed from inner caliper half. clean torque plate shaft and shaft bore in caliper, then apply special rubber grease to rubber bushing, wiper seal

iner surface, and torque plate shaft before reassembly. Tighten bridge bolts of caliper halves evenly.
Disassembly - Remove dust boot, retaining ring, stop washer, and piston stop bolt, and withdraw primary piston assembly, secondary piston assembly, and secondary return spring from master cylinder. NOTE - 
Do not disassemble primary piston assembly Remove check valve caps, tube seats, check valves, and check valve springs.
Inspection - Check master cylinder bore and piston for wear or other damage and replace as necessary. Check clearance between cylinder bore and piston; if clearance exceeds .006", replace parts as neccesary. Check all parts of secondary piston assembly; if any parts are found defective replace complete secondary piston assembly.

Reassembly - Reverse reassembly procedure and note the following. Apply rubber grease to all parts (except boots) before reassembly. When assembled, check that return part is not blocked by piston cup when piston is located at return position
Disassembly - 1) Hold front shell flange (master cylinder end of power unit) in a vice and remove clevis and lock nut. Scribe alignment mark on front and rear shells for reassembly reference. Holding neck of rear shell on both sides with pipes, remove rear shell by turning it counterclockwise. NOTE - The diaphragm spring can be removed at the same time. Remove diaphragm plate assembly from r
ear shell.
2) Using suitable driver, remove rear shell retainer and lift out bearing and valve body seal. Pull diaphragm plate assembly, then using a screwdriver, remove silenceDiaphragm plate is made of plastic and should be handled carefully at all times. Check push rod for damage and straightness. Check front and rear shells for cracks, damage and deformation. Repair or replace any defective part.

r retainer and lift out silencer and filter. Hold valve plunger, with key hole facing down and remove stop key by lightly pushing valve rod while shaking unit, then remove valve rod and plunger assembly. Remove reaction disc. NOTE - 
Reassembly - 1) Apply a sufficient amount of silicone grease to the following parts (see illustation): Front shell seal and push rod sliding surfaces (A); push rod and seal contact surface (C); outside surface of reaction disc (D); reaction disc inserting part of diaphragm plate (E); rear shell seal and diaphragm plate sliding surfaces (F); interior of piston plate into which plunger assembly is inserted and seal sliding surfaces (G).
2) Install seal and bearing into rear shell, then press in retainer. Gently install valve rod and pllunger, then install stoop key with chamffered end toward piston side. NOTE - After installing stop key, pull plunger assembly to ensure plunger is securely locked by stop key.Install reaction disc and diaphragm in diaphragm plate assembly, then install silencer filter and silencer into rear of diaphragm plate and press in retainer.

3) Install diaphragm plate assembly into rear shell, then install valve body guard (rear end first) into end of seal retainer. Install rear shell into front shell, then install push rod and front shell flange. Align marks made of disassembly, then turn rear shell until its notch touches stopper fully. Check clearance between power unit push rod and master cylinder piston (see illustration); clearance should be .30" (7.6mm) or less. If clearance is not to specifications, correct by adjusting push rod length. Install yoke onto threaded end of power unit operating rod.


Henry Jordan said...

Follow these easy steps to repair your brakes. These steps are excellent to perform this task. Thanks for sharing.

Henry Jordan

Hydraulic Seal Kits

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