How can you identify a vacuum leak in an engine?

Identifying a vacuum leak in an engine is crucial for maintaining optimal performance, as leaks can cause issues like rough idling and decreased fuel efficiency. Listening for a hissing sound is a common method since vacuum leaks often produce an audible noise as air enters the intake system. The use of a smoke machine further enhances this process by introducing smoke into the intake system. If there’s a crack or leak, the smoke will escape, making the source of the vacuum leak visually identifiable.

Other methods like checking the fuel lines for cracks or inspecting the oil dipstick do not directly assess vacuum integrity. Monitoring the temperature gauge during operation is also unrelated to vacuum leaks, as it focuses on engine temperature rather than air intake pathways. Thus, the combination of listening and the smoke test makes option B the most effective means of identifying a vacuum leak.