BRAKE OPERA TION

Air Brake System

This chassis features a dual braking system which has two complete air circuits: a primary circuit for rear brakes and a secondary circuit for front Each circuit receives air from separate Although there are two air they operate one brake system through the dual - circuit treadle This provides the driver with easy , graduated control when applying and releasing the

The air pressure the two circuits monitored gauges the instrument panel. When air pressure drops below 517 ± kPa (75 ± 5 psi) either system any time other than vehicle startup, pull the side the road and determine the problem. air pressure continues drop below ± 5 psi tractor the T railer Supply V alve (red octagonal knob) will immediately pop out the event a trailer breakaway sudden trailer air line which will apply the trailer spring the event a slow leak the trailer air the trailer supply valve will pop out when system Pressure reaches This protects the tractor air system from further pressure the T railer Supply V alve held in, attempt override application the trailer spring brakes, the Park Brake V alve (yellow diamond knob) will automatically pop out and apply the parking brakes when system pressure drops approximately psi.

BOTH systems, spring brakes will automatically apply . The Low Air Pressure W arning indicator and buzzer will activated low air pressure occurs either circuit.

The air brake system consists three main elements:

• The compressor , governor and reservoirs supply and store the air pressure.

• The brake application valve controls the brake application

• The brake chambers control the brake mechanism.

Air Brake Operation CAUTION

A void sudden stops. Constant, sudden stops may negatively affect the performance braking and driving parts.

When slowing for a stop, leave the clutch engaged for long possible use the braking fect the engine. When forward speed has dropped a little above idling speed, push clutch pedal and brake a complete stop.

Automatic Slack Adjusters

Automatic slack adjusters are designed automatically maintain proper brake chamber pushrod travel and compensate for brake lining wear during normal Manual adjustment automatic slack adjuster should never performed except when performing brake wheel service (such backing f the brake shoes for wheel brake shoe brake drum

When pushrod travel exceeds specifications (as given the "BRAKE ADJUSTMENT" section the Maintenance and Lubrication Manual,on a vehicle equipped with automatic slack adjusters, a mechanical problem with the slack adjuster , brake components improper installation the slack adjuster indicated. brakes are found out adjustment, the vehicle must taken the nearest repair facility have the problem investigated and corrected.

Danger

Automatic slack adjusters should not manually adjusted fort correct excessive pushrod stroke, because this condition indicates that a problem exists with the automatic adjuster , with the installation the adjuster , with related foundation brake components, which manual adjustment will not fix. Manual adjustment automatic slack adjusters a dangerous practice that could have serious consequences, because gives the operator a false sense security about the fectiveness the brakes, which are likely out adjustment again soon.

Parking Brake System

Spring - type parking brakes are standard all single and tandem rear axles. The spring brake system consists air cylinder with heavy springs, which integrated with the spring brake air chamber . When there pressure the air chamber , the springs expand (causing a brake application). When air pressure applied the air chamber , the springs are compressed (releasing the brakes).

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Parking Brake Operation

The parking brakes can applied and released from the cab, using the hand - operated push/pull control valve with the yellow diamond knob.

the event a significant air pressure loss both the air brake the spring brake air chambers will automatically exhausted (applying the The parking brakes will remain applied until enough pressure available recompress the

Parking W ARNING

• NEVER use the trailer parking brake system alone.

• NEVER use the tractor parking brake system alone.

• W A use the tractor and trailer parking brake systems together .

• W A apply the parking brakes when parking and make sur e the parking brakes e holding the vehicle moving befor e leaving the driver ’ s seat.

• When parking a grade, use wheel chocks under the r ear wheels turn the ont wheels the curb. not leave diesel engine vehicles gear; the vehicle should move, the engine may start heat compr ession.

• Check brake adjustment equently sur e that the brakes will lock and hold the vehicle when parked.

• not use the parking brake slow stop the vehicle when motion, except emergency .

• not use hand contr valve for parking.

Anti-Lock Brake System (ABS)

Note: Anti - lock brake systems became mandatory the U.S.A. all tractors beginning March 1997; all trucks beginning March and all trailers beginning March 2001. Federal regulations require that any tractor/truck with a trailer air connection built beginning March 2001 must have a data communications link with the trailer ABS and indicator lamp located the cab alert the driver there a trailer ABS

ABS Operation

When operating ABS - equipped vehicle, the following guidelines should used.

• Apply the brakes the anti - lock brake system begins maintain brake NOT release the

• A void rapidly pumping the brakes. The anti - lock brake system automatically applies and releases the brakes five times per second.

• When towing a trailer , watch the trailer through the Adjust brake application necessary keep the combination a straight Make sure the trailer follows the tractor properly

• amber trailer ABS lamp the instrument panel will illuminate for several seconds start - during initial function check. When a trailer ABS fault occurs, the lamp will remain illuminated until the fault cleared. there a loss communication between the tractor and trailer , the lamp will blink three times. Refer - Lock Brake System (ABS)” , page 130 for more information.

MACK Road Stability Advantage (If Equipped)

The MACK Road Stability Advantage (RSA) based the Bendix® ABS - 6 Advanced with ESP® (Electronic Stability Program) The RSA system aids the operator maintaining control the vehicle the event a jackknife rollover situation applying select brakes and reducing engine power required the specific situation. The RSA system, which integral with the anti - lock brake system, uses the standard ABS components (such wheel speed sensors and modulator valves) along with a Steering Angle Sensor (SAS60™) and a Y Rate/Lateral Acceleration Sensor60™) package provide information concerning vehicle movement the Advanced60™ Electronic Control Unit.

most vehicle repairs will not fect function the MACK RSA However , the following repairs require recalibration the SAS60™ sensor after the repair has been made:

• Removal and reinstallation replacement the SAS60™ sensor

Caution

Installation aftermarket steering wheel may damage the SAS60™ sensor . ther efor e r ecommended that the OEM steering wheel NOT r eplaced with aftermarket wheel.

• Any repairs the steering system front suspension such as:

Replacement front springs

Replacement king pins bushings

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