Automotive Service Excellence (ASE) A8 Engine PerformanceFuel, Air Induction, and Exhaust Systems Diagnosis and RepairEasy
A technician is diagnosing an engine with a noticeable exhaust 'tick' or 'putt-putt' sound, especially when cold. The sound is most pronounced near the exhaust manifold and tends to diminish slightly as the engine warms up. Which of the following is the MOST likely cause?
- AA leaking exhaust manifold gasket.
- BA restricted muffler.
- CA faulty oxygen sensor.
- DA clogged catalytic converter.
Show answer & explanationAnswer & explanation
Correct answer: A. A leaking exhaust manifold gasket.
A leaking exhaust manifold gasket is a common cause of an exhaust 'tick' or 'putt-putt' sound, particularly when the engine is cold. As the engine warms up, the metal components expand, which can temporarily reduce the leak and quiet the sound.
Why the other options are wrong
- B. A restricted muffler would cause excessive back pressure and a muffled, throaty sound, not a distinct tick from the manifold area.
- C. A faulty oxygen sensor affects engine performance and emissions but does not produce a mechanical ticking sound.
- D. A clogged catalytic converter would cause power loss and potentially a rotten egg smell, not a ticking sound from the manifold.
Exhaust Manifold Gasket Leak
A breach in the seal between the exhaust manifold and the cylinder head, allowing exhaust gases to escape.
- Often causes a ticking or 'putt-putt' sound.
- Sound typically louder when cold, may diminish as engine warms.
- Can lead to exhaust leaks before O2 sensor, affecting fuel trims.
Memory trick: Cold tick, manifold's trick, gasket's quick.