A combination vehicle is equipped with an Automatic Slack Adjuster. During a pre-trip inspection, you find that the pushrod stroke on one of the brake chambers exceeds the maximum allowable limit. What is the correct action to take?
- ATake the vehicle out of service and have the automatic slack adjuster inspected and repaired.
- BManually adjust the slack adjuster to bring the pushrod stroke within limits.
- CContinue the trip, as automatic slack adjusters will correct themselves during braking.
- DIncrease the air pressure in the system to reduce the pushrod stroke.
Show answer & explanationAnswer & explanation
Correct answer: A. Take the vehicle out of service and have the automatic slack adjuster inspected and repaired.
Automatic slack adjusters are designed to maintain correct pushrod stroke. If an automatic slack adjuster allows the stroke to exceed limits, it indicates a malfunction within the adjuster itself or other brake components. Manual adjustment of a faulty automatic slack adjuster is generally not recommended as a permanent fix and can mask a serious underlying problem. The vehicle must be taken out of service.
Why the other options are wrong
- B. Manually adjusting a faulty automatic slack adjuster is a temporary fix and can hide a serious underlying issue, making it unsafe.
- C. If the pushrod stroke is already excessive, the automatic adjuster is likely faulty and will not 'correct itself' to a safe operating range.
- D. Increasing air pressure will not correct an excessive pushrod stroke caused by a malfunctioning slack adjuster or other mechanical issues.
Faulty Automatic Slack Adjuster
If an automatic slack adjuster fails to maintain the correct pushrod stroke, allowing it to exceed legal limits, it indicates a malfunction that requires the vehicle to be taken out of service for inspection and repair, not manual adjustment.
- Automatic slack adjusters should self-adjust.
- Excessive stroke means a system defect.
- Manual adjustment is a band-aid for a broken auto-adjuster.
Memory trick: Auto-adjuster fails, 'Stop' the truck, 'Service' it now.