Automobile & Light Truck Certification Test A5 BrakesDrum Brake Diagnosis and RepairMedium
During a drum brake service, a technician notices that the automatic brake adjuster star wheel is seized and cannot be turned. The brake shoes are worn, but not excessively. What is the MOST likely consequence of this seized adjuster on vehicle braking performance?
- AIncreased noise during braking due to shoe drag.
- BImproved fuel economy due to reduced brake drag.
- CA low or spongy brake pedal.
- DPremature wear of the primary brake shoe.
Show answer & explanationAnswer & explanation
Correct answer: C. A low or spongy brake pedal.
A seized automatic adjuster means the brake shoes will not be properly advanced as they wear. This increases the distance the wheel cylinder pistons must travel to bring the shoes into contact with the drum, resulting in a low or spongy pedal feeling.
Why the other options are wrong
- A. Increased noise from drag would occur if the adjuster over-tightened the shoes, which is not the case here.
- B. Reduced brake drag from excessive clearance would lead to poor braking, not improved fuel economy as a primary symptom.
- D. Premature wear would be more likely if the shoes were constantly dragging, not if the adjuster seized in a 'loose' position.
Seized Auto Adjuster
A seized automatic brake adjuster prevents the brake shoes from advancing as they wear, leading to excessive shoe-to-drum clearance.
- Increases pedal travel.
- Causes low/spongy pedal.
- Reduces braking effectiveness.
Memory trick: Seized star wheel, pedal feels ill, braking's chill.