Automobile & Light Truck Certification Test A5 BrakesDrum Brake Diagnosis and RepairHard
A customer reports that their vehicle's parking brake does not hold the vehicle effectively on an incline, and the parking brake lever requires excessive travel to engage. The rear drum brakes were recently serviced, including shoe replacement and adjuster adjustment. What is the MOST likely cause of this continued issue?
- AContaminated brake fluid
- BOver-adjusted automatic adjusters
- CA faulty master cylinder
- DStretched parking brake cable
Show answer & explanationAnswer & explanation
Correct answer: D. Stretched parking brake cable
Even after a recent service, if the parking brake lever still requires excessive travel and doesn't hold, the most likely culprit is a stretched parking brake cable. While the automatic adjusters set the shoe-to-drum clearance for hydraulic braking, the parking brake cable itself needs separate adjustment to compensate for stretch over time, ensuring proper mechanical engagement.
Why the other options are wrong
- A. Contaminated brake fluid affects hydraulic braking, not the mechanical parking brake system.
- B. Over-adjusted adjusters would cause drag, not excessive lever travel without effective engagement.
- C. The master cylinder affects hydraulic braking, not the mechanical parking brake.
Stretched Parking Brake Cable
A parking brake cable that has elongated over time, leading to excessive lever travel and reduced holding force.
- Requires adjustment or replacement
- Causes poor parking brake performance
- Not resolved by drum brake shoe or adjuster service alone
Memory trick: Cable stretched, brake's fetched.