Examkin

Question

Difficulty: EasyBrake System Components Inspection

When inspecting foundation brake components, how should a driver properly check the free play on a manual slack adjuster?

  1. A
    Leave the parking brakes fully applied, pump the service brake pedal, and check that the pushrod does not move.
  2. B
    Drain all air tanks to zero pressure and measure the distance the slack adjuster falls under gravity.
  3. Chock the vehicle wheels, release the parking brakes, and pull firmly on each slack adjuster by hand.Answer
  4. D
    Keep the vehicle on a slight grade with parking brakes released and without wheel chocks to check roll resistance.

Answer

Chock the vehicle wheels, release the parking brakes, and pull firmly on each slack adjuster by hand.
To accurately measure the free play of a manual slack adjuster, the wheels must be securely chocked to prevent rolling, and the parking brakes must be released so the pushrod is not clamped by spring force. When pulled firmly by hand, the pushrod should not move more than about 1 inch1\text{ inch}.

Step-by-Step Solution

1
Secure the vehicle mechanically using wheel chocks on level ground.
The commercial vehicle cannot roll accidentally when air and parking brakes are released.
Safety is required before getting underneath or near wheels with released brakes.
2
Release the parking brakes from inside the cab to remove spring brake tension.
The brake shoes retract from the drum, freeing the pushrod mechanism.
Pushrod free play cannot be checked while the parking brake springs hold the linkage tight.
3
Pull firmly on each slack adjuster by hand or using a pry bar.
The pushrod movement is measured; it should not move more than about 1 inch1\text{ inch} (2.54 cm2.54\text{ cm}) where it attaches to the pushrod.
Excessive travel indicates that the manual brake assembly requires immediate adjustment.

Key Concept

Manual Slack Adjuster Inspection Procedure
Estimated Time:45s
Rate this question

Topics

Brake System Components Inspection

More questions from this topic