What procedure should be used to test for leaks in intake ducting?

• A. Engine running, use soap and water to detect leak
• B. Engine running, carefully feel for the leak
• C. Remove ducting, apply sealant, reassemble, use soap and water to detect leaks
• D. Engine running, use a digital pyrometer to locate hot leaking air

Answer: (C)

Testing leaks in intake ducting is about verifying a properly sealed, pressurized system so air escaping can be clearly observed. The correct approach is to remove the ducting to inspect and access the joints, apply the sealant where leaks are suspected, reassemble the ducting, and then run the engine while applying a soapy water solution to the joints to spot bubbling that shows escaping air. This sequence ensures you’re testing the actual assembled system under pressure, so any remaining leaks are detected reliably. Using soap and water with the engine running allows visible bubbles to indicate leaks, while simply feeling for leaks or using a temperature probe is unreliable or inappropriate for locating leaks.