* Cracked or damaged cylinder head gasket: This is the most common cause. The head gasket seals the combustion chambers from the coolant passages. A leak allows combustion gases (which smell like gas) and oil to contaminate the coolant.
* Cracked cylinder head or engine block: A crack in the engine block or cylinder head can also allow coolant to mix with oil and combustion gases. This is a much more severe problem than a blown head gasket.
* Oil cooler leak: If your engine has an oil cooler (common in many vehicles), a leak in the cooler can allow oil to contaminate the coolant.
* Transmission fluid leak (Automatic Transmission only): In some cases, a leak from the automatic transmission cooler (which is often integrated into the radiator) can lead to a smell that could be mistaken for oil or gas. This is less likely to result in a smell strongly resembling *gasoline*, however.
What to do:
* Do NOT drive the vehicle: Continuing to drive with this problem could cause serious engine damage.
* Have the vehicle inspected immediately by a qualified mechanic: They can diagnose the specific problem and recommend the necessary repairs. The longer you wait, the more extensive and expensive the repairs will likely be. The damage could progress to the point of requiring an engine rebuild or replacement.
The smell indicates a critical failure within the engine that needs professional attention. Ignoring it could lead to catastrophic engine failure.
