As a safety backup, the work brake system incorporates a feature that switches brake operation to the spring brakes if:

To apply the work brake:

FMVSS 121 requirements cover (but are not limited to) the following:

There are basic differences between straight truck and truck tractor air systems.

On CV model chassis, when ordered with additional air system capacity, the primary expansion reservoir is located on

MACK chassis now incorporate electronically operated air solenoid valves to direct air pressure to the various accessory air circuits such as: (mark all that apply)

If air pressure in either circuit drops below 70 psi, what should be done?

The spring brake modulating relay valve was implemented into production ________________ on CV model chassis, and was used on models ______ and ______ from the beginning of production.

On LE and MR models, the spring brake control valve allows a modulated application of the spring brakes through ________________ in the event of a primary air system pressure loss.

On tractor and trailer combinations, a tractor protection valve is used to prevent an air loss in the tractor air system should an air loss occur: ________________

At approximately 70 psi, sufficient pressure exists in the air system to shut off the low air buzzer and the low air warning lamp. When the parking brake valve is pushed IN;

Many chassis are equipped with a relay valve that speeds up the application of the rear service brakes by providing reservoir pressure: ________________

15. Exhausting air through the relay valve allows the brakes to release more quickly than _______________.

16. Air in the line between the _______________ and the _______________ exhausts through the treadle valve.

17. Air-actuated brakes are _______________ on all MACK chassis.

All MACK chassis use a dual air system which is _______________ with either system capable of stopping the vehicle should one system fail.

What is the supply reservoir also called because it traps moisture, oil, etc.?

Different reservoir configurations are available, depending upon chassis model.

It is the responsibility of the body/equipment installer/alterer to ensure that the chassis remains in compliance with U.S. Federal and Canada Motor Vehicle Safety Standards _______ and _______ when modifications are made to the air brake system.

It is recommended that ____________ plastic air line tubing be used for ____________ __________________ lines.

U.S. Federal and ________________ Motor Vehicle Safety Standard (MVSS) 121 requires that total air capacity for the vehicle must be 12 times the total volume of all air chambers.

Applying the work brake while the vehicle is in motion, can lead to _______________________________ and loss of vehicle control could occur, especially on _______________________________. In addition, the force of the stop could cause the operator to be _______________________________.

With foot pressure applied, the brake pedal on a vehicle with vacuum assisted power brakes moves down slightly when the engine is started. Technician A says this condition can be caused by a leaking power brake booster diaphragm. Technician B says the cause could be a faulty power brake booster check valve. Who is right?

Which component in the Hydro-Boost system provides power assist if there is a loss of hydraulic pressure to the system?