The inability of the compressor to produce a high ______ indicates an intake valve leak.

• A. Vacuum
• B. Pressure
• C. Flow
• D. Temperature

Answer: (A)

Intake valves must seal tightly to let the piston create a deep vacuum on the suction side during the intake stroke. If the intake valve leaks, some of the suction gas leaks past the valve, preventing the cylinder pressure from dropping far enough. That means the compressor cannot develop a high vacuum as it should. So, a symptom of an intake valve leak is the inability to achieve a high vacuum on the suction side.

High pressure, flow, or temperature aren’t the specific indicators of this leak. A valve leak on the intake side primarily shows up as reduced vacuum rather than an outright rise in pressure, and it doesn’t directly dictate a temperature change or a distinct flow abnormality compared with the vacuum signal.