Which test can be performed to detect a vacuum leak?

A smoke test is an effective method for detecting a vacuum leak in an engine's intake system. This test works by introducing smoke into the intake manifold or vacuum lines under a controlled environment. If there are any leaks, the smoke will escape from the areas where the vacuum is compromised, making it visible to the technician. This visibility allows for pinpointing the exact location of the leaks, which can then be repaired to ensure the engine operates efficiently and maintains the appropriate air-fuel mixture.

In contrast, a compression test measures the pressure within the engine's cylinders to evaluate the health of the piston rings and valves, which does not specifically identify vacuum leaks. A voltage drop test is used to assess the integrity of electrical circuits and connections, which is not related to vacuum systems. Similarly, a coolant pressure test evaluates the integrity of the cooling system, including the radiator and head gasket, but does not address vacuum concerns. Each of these tests serves a different diagnostic purpose, making the smoke test particularly suited for finding vacuum leaks.