Automotive Service Excellence (ASE) A8 Engine PerformanceFuel, Air Induction, and Exhaust Systems Diagnosis and RepairEasy
A technician is performing a smoke test on a vehicle's exhaust system to locate a suspected leak. Where should the smoke typically be introduced for an effective test?
- AInto the tailpipe, with the engine off and exhaust blocked.
- BInto the exhaust manifold, with the engine off.
- CInto the tailpipe, with the engine running at idle.
- DInto the muffler inlet, with the engine running.
Show answer & explanationAnswer & explanation
Correct answer: A. Into the tailpipe, with the engine off and exhaust blocked.
For an exhaust smoke test, smoke is introduced at the tailpipe with the engine off and the tailpipe blocked to pressurize the system and reveal leaks.
Why the other options are wrong
- B. Introducing smoke directly into the manifold might be too far upstream, and the engine must be off.
- C. Running the engine would expel the smoke, making it ineffective for leak detection.
- D. Running the engine would prevent proper pressurization and make leak detection difficult.
Exhaust System Smoke Test
A diagnostic procedure used to locate leaks in the exhaust system by introducing smoke under pressure.
- Engine must be off to prevent smoke expulsion.
- Tailpipe must be blocked to pressurize the system.
- Smoke is introduced into the tailpipe or a convenient access point.
Memory trick: Smoke in, engine off, tailpipe tight, leaks in sight.