79. How do you test the hydraulic brakes for leaks?
Detailed Explanation
The correct answer is "Pump the brake pedal three times, then apply firm pressure to the pedal and hold for five seconds. The pedal should not move.". This question tests controlled braking, heat management, and maintaining steering control. For a differently worded version of this question, identify the hazard first and then choose the answer that preserves control, visibility, or legal compliance.
Correct Answer: Pump the brake pedal three times, then apply firm pressure to the pedal and hold for five seconds. The pedal should not move.
Why This Matters on the CDL Test
This question belongs in your brake safety review. Pay close attention to pressure limits, inspection steps, stopping distance, and warning signs because brake-system mistakes are a common reason CDL applicants miss endorsement questions.
How to Remember It
Say the rule in your own words, then explain why the wrong answers are unsafe or incomplete. That habit makes similar Air Brakes questions easier when the exam changes the wording.
Answer Review
Choose "Pump the brake pedal three times, then apply firm pressure to the pedal and hold for five seconds. The pedal should not move." because this answer matches the safe CDL action for brake system safety. On the knowledge test, the safest answer is usually the one that protects space, control, visibility, legal compliance, or inspection accuracy before the vehicle is put at risk.
Why the other answers are weaker
- Drive slowly and pump the brake pedal. Make sure it doesn't hit the floor."Drive slowly and pump the brake pedal. Make sure it doesn't hit the floor." does not best answer this brake system safety question. When you see a similar option on the CDL permit test, compare it against the exact safety rule and choose the answer that prevents the most immediate risk.
- Drive 20 mph and slam on the brakes."Drive 20 mph and slam on the brakes." does not best answer this brake system safety question. When you see a similar option on the CDL permit test, compare it against the exact safety rule and choose the answer that prevents the most immediate risk.
Test-Day Checklist
- Read the question once for the topic, then read it again for the exact CDL action being tested in Air Brakes.
- Eliminate answers that sound convenient but skip an inspection, warning sign, or safety step.
- Say the correct rule out loud before moving on so you can recognize it when the exam changes the wording.
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Start Practice TestRelated Questions
22. Total stopping distance for air brakes is longer than that for hydraulic brakes due to distance.
104. How should you check that your service brakes are working properly?
105. How should you check that the service brakes come on when air pressure in the system drops below a certain level?
110. To check the brake slack on S-cam brakes, you should park on:
14. During normal driving, spring brakes are usually held back by:
Keep Studying Air Brakes
Question pages help you review one rule at a time. To build test-day speed, move back into the full Air Brakes practice test and answer a mixed set without looking at the explanation first.
State CDL Practice Paths
After you understand this answer, use a state practice path to connect the federal CDL rule with the DMV test pages drivers search for most.