Automobile & Light Truck Certification Test A5 BrakesHydraulic System Diagnosis and RepairMedium
A technician is performing a brake system inspection and notices that the brake fluid reservoir cap is missing. The fluid level is low and appears dark. Which of the following is the most appropriate immediate action?
- ATop off the reservoir with new DOT 3 brake fluid and advise the customer to monitor.
- BInspect for leaks, replace the cap, and then perform a complete fluid flush.
- CReplace the brake fluid reservoir cap and perform a complete fluid flush.
- DBleed the entire brake system to remove air and contaminated fluid.
Show answer & explanationAnswer & explanation
Correct answer: B. Inspect for leaks, replace the cap, and then perform a complete fluid flush.
A missing cap allows moisture and contaminants into the system, degrading the fluid. Low fluid indicates a potential leak. The most appropriate action is to first address the leak, then replace the cap, and finally flush the contaminated fluid.
Why the other options are wrong
- A. Topping off without addressing the cause of low fluid and contamination is insufficient and potentially unsafe.
- C. Replacing the cap and flushing is good, but a low fluid level always warrants a leak inspection first.
- D. Bleeding is part of a flush, but without checking for leaks and replacing the cap first, the problem will recur.
Brake Fluid Contamination & Loss
Brake fluid can become contaminated by moisture and debris, especially with a missing cap, leading to reduced performance. Low fluid often indicates a leak.
- Missing cap allows moisture entry
- Moisture degrades fluid (lowers boiling point)
- Low fluid suggests a leak
Memory trick: Cap missing, fluid low, check for leaks, then let the new fluid flow!