DIAGNOSE - EXHAUST FUMES IN PASSENGER COMPARTMENT

By Carl O'Reilly

SYMPTOM SUMMARY
Exhaust fumes are present in the passenger compartment. The condition may be worse while the air conditioning or heater is on.

USUAL CAUSE
The usual cause of this symptom is an exhaust leak. Exhaust fumes can enter the passenger compartment from the heater and air conditioning vents.

DIAGNOSIS
An inspection of the exhaust system will be necessary. Focus your inspection on the exhaust manifold gaskets and the gaskets that attach the exhaust pipe to the manifold. If either of these gaskets are leaking, exhaust fumes can enter the passenger compartment. Inspect for broken or missing exhaust manifold bolts. Inspect the exhaust system beneath the vehicle for damage or leaks. Inspect the muffler and catalytic converter to ensure they are intact and leak free. Often, an exhaust leak will create a spitting sound when the engine is cold and will diminish after the engine has reached operating temperature. Pinpointing the leak when the engine is cold may be easier.

CORRECTIVE ACTION
Once the source of the exhaust leak has been pinpointed, the exhaust system will have to be repaired.

PRECAUTIONS, TIPS, and NOTES
You should use extreme caution when working around hot or rotating engine parts. If service to the exhaust manifold is required, it is recommended that the manifold bolts be sprayed with a penetrating oil prior to removal. Allowing the bolts to soak for 15 to 20 minutes will also aid in the removal. Work on the exhaust system should be performed when the engine is cold.