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

When slowing for a leave the clutch engaged for long possible use the braking fect the When forward speed has dropped a little above idling push clutch pedal and brake a complete https://www.truck-manuals.net/

Automatic Slack Adjusters

Automatic slack adjusters are designed automatically maintain proper brake chamber pushrod travel and compensate for brake lining wear during normal use. Manual adjustment automatic slack adjuster should never performed except when performing brake wheel service (such backing f the brake shoes for wheel removal, brake shoe relining/replacement, brake drum reconditioning, etc.).

When pushrod travel exceeds specifications (as given the "BRAKE ADJUSTMENT" section the Maintenance and Lubrication TS494) a vehicle equipped with automatic slack a mechanical problem with the slack adjuster , brake components improper installation the slack adjuster brakes are found out 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 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).

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 all tractors beginning March 1997; all trucks beginning March 1998, and all trailers beginning March 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 malfunction. ABS

Operation

When operating ABS - equipped the following guidelines should

• Apply the brakes normal. the anti - lock brake system begins function, maintain brake pressure. NOT release the brakes.

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

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

• amber trailer ABS lamp the instrument panel will illuminate for several seconds start - during initial function When a trailer ABS fault the lamp will remain illuminated until the fault there a loss communication between the tractor and trailer , the lamp will blink three Refer - Lock Brake System (ABS)” , page 155 for more

MACK Road Stability Advantage (If Equipped)

The MACK Road Stability Advantage (RSA) based the Bendix® ABS - 6 Advanced with ESP® (Electronic Stability Program) System. 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 most cases, vehicle repairs will not fect function the MACK RSA system. 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

• Any repairs the steering system front suspension such as:

Replacement front springs

Replacement king pins bushings

Replacement the steering gear

Replacement the drag cross steering tube ball sockets

Replacement the front spring hangers

Replacement the steering column

• Front end alignment

• Disconnecting the steering column from the steering gear , the steering linkage from the steering gear

W Arning

Failur e r ecalibrate the steering angle sensor after performing any the r epairs mentioned above, may affect oper function the RSA system, r esulting a loss vehicle contr due system intervention inappr opriate times.

V ehicle Modifications

Alterations the such changes the wheel base (either lengthening the addition auxiliary lift axle removal a factory - installed auxiliary lift major body such conversion a tractor a truck suspension steering system component are NOT these changes will adversely fect performance the road stability Should such changes the system must disabled having a qualified technician replace the Advanced60™ ECU with a Premium60™

W Arning

Failur e disable the RSA system a vehicle that has been modified will r esult serious vehicle braking and performance issues, including unnecessary system interventions. These interventions could lead a loss vehicle contr ol.

addition disabling the system, any cab labels, such warning and caution labels r elating the Bendix® ABS - 6 Advanced with ESP® system located the sun visor must r emoved, and notations must made the operator ’ s manuals that the vehicle operator has a clear understanding which ABS options e installed the vehicle.

Location the yaw rate/lateral acceleration sensor must not altered. When servicing required, the sensors must replaced with identical components using the original equipment mounting brackets and tightening torque specifications (20 N.m [15ft]).

The following additional changes MUST NOT made - vehicle:

• Changes maximum steering angle (to the left right)

• Changes steer axle and/or drive axle track width

• Changing the front and/or rear brake drums drums having a dif ferent flange thickness

T ire Size Calibration

The ECU requires a precise rolling circumference ratio between the front steer axle and the rear drive axles for optimum performance the system. For this reason, the system continuously calculates the precise ratio and stores the information the ECU memory .

Caution

Effectiveness the RSA system r elies the accuracy the r eported vehicle major changes tir e sizes e such that changes the vehicle speedometer/odometer settings e r equir the Advanced60™ ECU must r epr ogrammed with the new values a qualified

Enhanced Stability Program

Enhanced Stability Program (ESP) optional system that uses existing ABS and A components with the addition electronic sensors and brake valves. The system will automatically apply and release individual brakes improve vehicle control when extreme conditions are detected. the event a pending rollover situation sensed, the system applies all brakes reduce vehicle speed lessen the possibility rollover . Please refer the applicable vendor manual for more information.

Precautions When Installing Electrical Equipment

Connecting electrically powered electrically controlled equipment the vehicle may cause interference with other vehicle components the ABS The amount interference will depend the operating frequency any new signals and the degree which transient signals are coupled into the vehicle

Note: Whenever new electrical equipment the obligation the installer ensure that the new equipment does not interfere with the proper operation all other electrical systems the new electrical equipment a vehicle checkout procedure should

Perform the checkout procedure under the following conditions:

• Engine running

• Brake system air pressure operating range

• V ehicle stationary

• Brake pedal fully depressed

Operate the new equipment under all running and shutdown

Listen for signs air exhausting from ABS modulator valves (which indication interference condition).

Correct all interference conditions before operating the vehicle.

Note: The center pin the standard seven - pin trailer electrical connector has been standardized the dedicated connection for uninterrupted power for trailer This pin always hot when the tractor ignition turned on. https://www.truck-manuals.net/

Danger

Some trailers manufactured prior the trailer ABS regulations may use the center pin power certain trailer auxiliary equipment. The possibility exists that this auxiliary equipment may unexpectedly activated the truck tractor electrical system, resulting personal injury damage equipment. Caution must used when connecting the trailer electrical connector ensure that power the center pin will not unintentionally activate any trailer auxiliary equipment.

Automatic T raction Control TC) (If Equipped)

Automatic T raction Control TC) provides improved traction slippery surfaces reducing wheel spin. The system operates automatically follows:

• a drive wheel starts A applies air pressure the brake the spinning Doing this transfers engine torque the wheels that have better

• all drive wheels are spinning, A limits engine torque which, turn, reduces wheel spin provide improved traction.

When A automatically becomes the A indicator lamp turns alert the operator The lamp turns f when the wheel(s) stops

Heavy Mud/Snow Function (If Equipped)

A may also include a heavy mud/snow function which allows the operator activate A when additional traction needed. This function activated with the A mode switch which located the dashboard. The heavy mud/snow function increases available traction increasing permissible wheel spin.

When the operator selects the heavy mud/snow function, the A indicator lamp blinks continuously . The A lamp stops blinking when the A mode switch turned