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General Smog Check

Cracked Exhaust Manifold Causes Smog Failure

My Mercedes E320 has a crack in the exhaust pipe near the exhaust manifold. I need to know if this will cause it to fail the smog check. The crack is loud enough to hear, but barely visible. Thank you in advance.


A cracked exhaust manifold or exhaust pipe (which is located before the catalytic converter) will cause, at the least, a smog check visual failure. Your vehicle's exhaust components are part its emissions system, subsequently, inspected during the smog inspection. Any defect, damage, or modification will cause the vehicle to fail the smog test.

Furthermore, there is a great likelihood that the exhaust system crack, whether it be located at or on the exhaust manifold, or exhaust pipe before the catalytic converter, will cause fresh air to be added to the exhaust stream disrupting the air to fuel ratio required for proper catalytic converter operation. The CAT needs a 14.7:1 air/fuel ratio in order to effectively reduce the chemical components in a vehicle's exhaust which make up smog.

posted by SmogTips Support

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