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Adjusting Service Brakes
Bleeding Brake System
Brake Hose and Tubing
Master Cylinder Fluid Level
Stop Lamp Switch Adjustment
Test for Fluid Contamination
Testing Application Adjuster Operation
Wheel Stud Nut Tightening
Normally self adjusting drum brakes will not require manual adjustment but in the event of a brake reline it is advisable to make the initial adjustment manually to speed up the adjusting time.
(1) Jack up vehicle so all wheels are free to turn.
(2) Remove rear adjusting hole plugs from brake supports of vehicle.
(3) Be sure parking brake lever is fully released, then back off parking brake cable adjustment so there is slack in cable.
(4) Insert adjusting tool C-3784, into star wheel of adjusting screw. Move handle of tool upward until a slight drag is felt when road wheel is rotated.
(5) Insert a thin screwdriver or piece of welding rod into brake adjusting hole and push adjusting lever out of engagement with star wheel (models with Iso-Clamp rear suspension, bend welding rod to match adjusting tool angles plus a 3/4 reverse bend at contact end), (Fig. 1). Care should be taken so as not to bend adjusting lever or distort lever spring. While holding adjusting lever out of engagement, back off star wheel to insure a free wheel with no brake shoe drag.
(6) Repeat above adjustment at each wheel. The adjustment must be equal to all wheels. Install adjusting hole plugs in brake supports.
(7) Adjust parking brake after wheel brake adjustment.
It is important to follow the above sequence to avoid the possibility of the parking brake system causing brake drag, if the parking brakes are adjusted before the service brakes.
Place the vehicle on a hoist, with a helper in the driver�s seat to apply the brakes. Remove the access plug from the rear adjustment slot in each brake support plate to provide access to the adjuster star wheel. Then, to eliminate the possibility of maximum adjustment, whereby the adjuster does not operate because the closest possible adjustment has been reached, back the star wheel off approximately 30 notches. It will be necessary to hold the adjuster lever away from the star wheel to permit this adjustment.
Spin the wheel and brake drum in the reverse direction and with greater than normal force apply the brakes suddenly. This sudden application of force will cause the secondary brake shoe to leave the anchor. The wrap up effect will move the secondary shoe, and the cable will pull the adjuster lever up. Upon application of the brake pedal, the lever should move upward, turning the star wheel. Thus, a definite rotation of the adjuster star wheel can be observed if the automatic adjuster is working properly. If one or more adjusters do not function properly, the respective drum must be removed for adjuster servicing.
MASTER CYLINDER FLUID LEVEL
Check the fluid level in the master cylinder twice a year. The master cylinder black nylon reservoir is marked with the words �fill to bottom of rings� indicating proper fluid level. Remove the caps to check the level. Wipe caps and reservoir clean to prevent dirt and foreign matter from dropping into the reservoir.
If necessary, add fluid to bring level to bottom of rings in reservoir. With disc brakes, fluid level can be expected to fall as the brake pads wear. Use only brake fluid conforming to DOT 3. MOPAR Brake Fluid is a fluid of this quality and is recommended to provide best brake performance. Use of a brake fluid that may have a lower Initial boiling point, such as fluid Identified as 70R1 or unidentified as to specification may result in sudden brake failure during hard prolonged braking. Use only brake fluid that has been stored in a tightly closed container, to avoid contamination with foreign matter or moisture.
CAUTION: Do not allow petroleum base fluid to contaminate the brake fluid. Seal damage will result.
BLEEDING BRAKE SYSTEM
Clean all dirt and foreign material from the cover of the master cylinder to prevent dirt from falling into the master cylinder� reservoir when the cover is removed.
Using the one man bleeder tank C-3496-B (with adapter C-4578) provides a convenient means for pressurizing the hydraulic system for bleeding. (Complete bleeding of the dual master cylinder is important! See Bleeding the Master Cylinder in this Group.)
Starting with the right rear wheel clean all dirt from the bleeder valve. Place bleeder hose on the bleeder valve and insert the other end of the bleeder hose into a clear jar half filled with clean brake fluid. (This will permit the observation of air bubbles as they are being expelled from the hydraulic system and also prevent air from being drawn back into the system. Follow the manufacturers instructions in the use of the bleeder tools).
Continue this bleeding operation with the left rear wheel, then the right front and finishing with the left front wheel.
If necessary, repeat this bleeding operation if there is any indication (a spongy brake pedal or warning light) of air remaining in the hydraulic system.
Brake System Bleeding Procedures
All vehicles are equipped with a pressure holdoff valve. The valve is located (in the combination valve) on the left side of the engine compartment. The use of the hold-off valve is to better match front disc brakes with the rear drum brakes, resulting in improved braking and steering control on icy surfaces.
Due to operating characteristics of the valve, which causes complete shut-off of the flow of brake fluid between approximately 3 and 135
psi, front brake bleeding procedures should be done as follows:
(1) Gravity Bleed: This method of bleeding is not affected by the hold-off valve, as fluid pressures are always below 3 psi. Remove master cylinder reservoir cover and gasket, then fill reservoirs with approved brake fluid. Open disc brake bleeder screws, and allow fluid and air to drain until stream of fluid is free of air.
(2) Pedal Bleed: This method of bleeding is not affected by the hold-off valve, as fluid pressures are in excess of 135 psi. Follow normal procedure of pumping pedal and opening bleeder screws. Do not pump master cylinder dry!
(3) Pressure Bleed: This method of bleeding is influenced by the hold-off valve. Bleed pressure, normally about 35 psi, is high enough to cause the hold-off valve to close, stopping the flow of fluid to the front brakes. However, the valve (Fig. 2) must be held open manually by using Tool C-4121, to pull the valve stem out.
CAUTION: Under no condition should a rigid clamp, wedge or block be used to depress the valve stem, as this can cause an internal failure in the valve, resulting in complete loss of front brakes.
It should be noted that the pressure release valve stem is in its innermost position when there is no pressure present. No attempt should be made to further depress the valve stem.
If diagnosis determines that master cylinder alone is cause of trouble, it can be replaced without bleeding the hydraulic system provided the replacement cylinder is completely bled before installation. (See - Bleeding Master Cylinder). After brake tubes are connected, have helper apply force to pedal while both tube nuts are cracked to release any air and then retightened.
TEST FOR FLUID CONTAMINATION
Swollen rubber parts indicate the presence of petroleum in the brake fluid. To confirm that contamination exists, make the following test.
Place a small amount of the drained brake fluid into a small clear glass bottle. Separation of the fluid into distinct layers will indicate mineral oil content.
If there is any question of mineral oil content, drain system, flush thoroughly and replace all rubber parts.
WHEEL STUD NUT TIGHTENING
The tightening sequence and torquing of the wheel stud nuts is of great importance to insure efficient brake operation. The use of an impact or long handled wrench may distort the drum.
Use a criss-cross tightening sequence (Fig. 3). Tighten all the stud nuts to one-half the specified torque first, and then repeat the sequence tightening to the specified 85 ft. lbs. (115 N�m)
BRAKE HOSE AND TUBING
Inspection of Brake Hose and Tubing
Flexible rubber hose is used at both front brakes and at a rear axle junction block.
Inspection of brake hoses should be performed whenever the brake system is serviced and every 7,500 miles or 12 months, whichever comes first (every engine oil change). Inspect hydraulic brake hoses for severe surface cracking, scuffing, or worn spots. Should the fabric casing of the rubber hose be exposed due to cracks or abrasions in the rubber hose cover, the hose should be replaced immediately! Eventual deterioration of the hose can take place with possible burst failure.
Faulty installation can cause twisting, and wheel, tire or chassis interference.
Installation of Brake Hose
Always use factory recommended hose to insure quality, correct length and superior fatigue life. Care should be taken to make sure that the tube and hose mating surfaces are clean and free from nicks and burrs. Right and left brake hoses are not interchangeable.
Use new copper seal washers and all connections should be tight and properly made.
The flexible hydraulic brake hose should always be installed on the vehicle by first tightening the block end of the hose onto caliper, or rear axle housing tee. The intermediate bracket should then be bolted to the suspension �k� member. The hose should then be attached to the hose bracket in a manner to give minimum twist with the wheel in a straight ahead position. (15 degrees twist is the maximum recommended). Excessive twist can result in hose interference problems with possible hydraulic system failure. Finally, the tube is attached to the hose.
Repair and Installation of Brake Tubing
Double wall steel tubing should always be used for replacement. Care should be taken when replacing brake tubing to use the proper bending and flaring tools and to avoid kinking or routing the tubes against sharp edges, moving components or in hot areas. All tubes should be properly attached with recommended retaining clips.
Steel tubing is used to conduct hydraulic pressure to the front and rear brakes. Steel tubing is used from the junction block to both rear wheel cylinders. All fittings, tubing and hoses should be inspected for rusted, damaged or defective flaring seats. The steel tubing is equipped with a double flare inverted seat to insure more positive seating in the fitting. To repair or reflare tubing proceed as follows:
(1) Using Tool C-3478-A, or equivalent, cut off damaged seat or damaged tubing (Fig. 4).
(2) Ream out any burred or rough edges showing on inside edges of tubing. This will make the ends of tubing square and insure better seating of flared end tubing. Place tube nut on tubing prior to flaring tubing.
(3) To flare tubing open handles of flaring Tool C-4047 and rotate jaws of tool until the mating jaws of tubing size are centered in area between vertical posts.
(4) Slowly close handles with tubing inserted in jaws but do not apply heavy pressure to handle as this will lock tubing in place.
(5) Place gauge �Form A� on edge over end of tubing and push tubing through jaws until end of tubing contacts the recessed notch of gauge matching the size of tubing (Fig. 4).
(6) Squeeze handles of flaring tool and lock tubing in place.
(7) Place 3/16 inch plug of gauge �A� down in end of tubing. Swing compression disc over gauge and center tapered flaring screw in recess of disc.
(8) Screw in until plug gauge has seated on jaws of flaring tool. This action has started to invert the extended end of the tubing.
(9) Remove gauge and continue to screw down until tool is firmly seated in tubing.
(10) Remove tubing from flaring tool and inspect seat.
STOP LAMP SWITCH ADJUSTMENT
The stop lamp (or stop lamp/speed control) switch and mounting bracket assembly is attached to the brake pedal bracket. The switch is actuated by the brake pedal blade on all models.
Refer to figure 5 for proper switch adjustment as follows:
(1) Loosen switch assembly to pedal bracket attaching screw and slide assembly away from pedal blade or striker plate.
(2) Push brake pedal down and allow to return to free position, do not pull brake pedal back at any time.
(3) Place proper spacer gauge on pedal blade. A clearance of .130 to .150 inch required for the heavy duty stop lamp switch, and .060 to .080 inch for the stop lamp/speed control switch.
(4) Slide switch assembly toward pedal blade until switch plunger is fully depressed against spacer gauge (on heavy duty or stop light/speed control switches, depress plunger until switch body contacts spacer gauge).
(5) Re-tighten switch bracket screw to 75 in. lbs. (8 N�m).
(6) Remove spacer. Be sure that stop lamp switch does not prevent full pedal return.
Basic Diagnosis Guide
|Brake Warning Light "On"||X||NO||O|
|Excessive Pedal Travel - Spongy Pedal||X||NO||O|
|Pedal Goes to Floor||6||X||O|
|Stop Light "On" All The Time||3||O|
|Brakes Drag - Front or All||5||X||O|
|Rear Brakes Drag||2||NO|
|Excessive Pedal Effort||1||X||O|
|Rough Engine Idle||O|
|Brake Chatter (Rough)||NO||NO||X|
|Surge During Braking||NO||NO||X|
|Noise During Braking||NO||X|
|Pedal Pulses During Braking||NO||NO||X|
|Rattle or Clunking Noise||NO||X|
|Premature Rear Wheel Lockup||4||NO||NO|
|Pull to Right or Left||NO||NO||X||X|
X - Most Likely Cause O - Possible Cause NO - Not Possible Cause
All the time
Blocked or pinched rear line or hose
Poor vacuum supply to booster
Dragging brakes - see 2 and 5
Only after several stops
Excessive use, riding brakes, mountain descent in high gear
Rear brakes drag
Parking brake dragging, check adjustment
Weak return springs
Contaminated fluid or lining
Stop lights on all the time
Inspect for correct pedal linkage
Inspect for binding stop light switch adjustment
Premature rear wheel lockup
Contaminated rear lining, inspect
Inoperative proportion valve, test
Front or all brakes drag
Misadjusted stop light switch - prevents full pedal return
Contaminated fluid - seals swollen
Pedal or linkage binding or incorrectly assembled
Booster defect (very rare)
Pedal goes to floor, warning lamp does not light
Booster runout (Maximum Assist Point) is often mistaken for the pedal hitting the floor,
especially when the car is not moving. The change in pedal effort at runout is interpreted as
bottoming the pedal. Check by opening and closing a fitting and allowing the pedal to move.
Brake Chart 2 - Actuation Diagnosis
Warning Light (Ignition On)
Light "on" indicating malfunction
Remove master cylinder reservoir caps - check fluid level
Fluid level OK
Examine diaphragm and fluid for signs of contamination, diaphragm swollen, etc
Replace fluid and all rubber parts per service manual
See "Basic Hydraulic Test", below in this chart
Fluid level low (below reservoir seam)
Check entire system for leaks
Repair or replace as required
Check warning light circuit
Apply parking brake - ignition in Run position
Warning light on
Parking brake released - light off
Check wire connected to warning switch in engine compartment
See "Basic Hydraulic Test", below in this chart
Warning light off
Check and repair electrical circuit as required
Basic Hydraulic Test
Ignition in Run position, pump brakes five times with engine off. Then apply brake pedal very slowly.
Gradually increase pedal effort while watching warning light, increase to very high effort (both feet),
hold heavy effort for 30 seconds, release pedal slowly.
Warning light comes on with moderate pedal effort and stays on when pedal is released
Master cylinder has internal leak, replace and bleed brakes
Warning light comes on at moderate to heavy pressure but goes out when pedal is released
Air in system. the greater pedal effort required to get the light on, the less air in the system,
Warning light does not come on - system has no defect!
Bleeding or adjusting rear brakes may make some improvement. If less than 1000 miles on
car, additional mileage will help. If pedal pumps up but becomes low after left or right turns,
loose front wheel bearings may be the problem.
Warning light comes on only after holding heavy pedal effort for several seconds, and pedal
moves down under constant heavy effort
Small high pressure leak in system. Repeat test several times and look for wet area.
Repair and bleed.
Brake Chart 4 - Brake Noise Diagnosis
Engine Noise Location
Brake Chart 5 - Wheel Brakes Diagnosis
Pulls during normal braking
See Chart 6.
Pulls with no braking or with very heavy braking
See "Front Suspension" section of service manual.
Excessive pedal travel after turns
Loose front wheel bearings
Pedal pulses, car surges during braking, brake chatter
Disconnect and plug master cylinder outlet to rear brakes
Surging or pulsing still present
Inspect front brakes for disc thickness variation and runout, check bearing adjustment
No vibration or pulsing
Inspect rear brakes for out of round *
* Pulsation caused by rear brakes may be eliminated or reduced by indexing drum (rear) two studs on
Brake Chart 6 - Brake Pull Diagnosis
Pulls to One Side During Normal (Light) Braking
Check for unequal front brake drag, open and close bleeders and recheck
Inspect front end for looses attachments, including steering gear mounting bolts and worn or
Inspect front brakes
Inspect front end height and cross shaft adjustment
Replace front linings
Plug rear brakes and road test front brakes only
Pulls or leads with no brakes, pulls on hard braking only
See "Front Suspension" section of service manual.
Inspect rear brakes & parking brake. Repair as required
Defects or problems found
Repair as required
Grease on rotors, fluid leaks, damage
Repair as required
Drag affected by hydraulic pressure
See Chart 1 and Chart 5
Repair or replace as required
Check calipers, pry back pistons, adapter ways, etc
Repair or replace caliper
Make sure that whenever a
brake part is replaced or a brake repair is completed, the vehicle is