What would indicate that Technician B's assumption about the power brake booster check valve is correct?

• A. The brake does not engage
• B. The booster diaphragm has a leak
• C. The vehicle exhibits issues only when the engine is off
• D. Brake pressure is inconsistent

Answer: (C)

The correct answer highlights that the vehicle exhibits issues only when the engine is off, which would indicate that Technician B's assumption about the power brake booster check valve is correct. The check valve is designed to maintain vacuum in the booster system to assist with braking power when the engine is off. If the vehicle experiences braking issues exclusively when the engine is not running, it suggests that the booster is not holding the necessary vacuum, leading to reduced brake power.

This scenario points toward the functionality of the check valve because, when the engine is off, there should still be adequate vacuum in the system if the check valve operates properly. If it is malfunctioning, the driver would notice a significant difference in brake feel and an increase in pedal effort, confirming the assumption about the power brake booster check valve.

Other options indicate issues that may be related to different parts of the braking system rather than specifically pointing to the check valve's performance. For instance, if the brake does not engage at all, it could imply a failure in the entire braking system or another component entirely. Similarly, a leaking booster diaphragm would indicate a different type of failure unrelated to the check valve, and inconsistent brake pressure might suggest a problem elsewhere in the brake system, not just tied to the booster