Mercedes-Benz S420 Exhaust fume odor in car Inspection at your home or office.

Common reasons for this to happen:

• Exhaust Leak: If the exhaust smell is inside the vehicle cabin, a leak in the exhaust system is almost always the cause. A leak can develop anywhere in the exhaust system and this can result in a heavy exhaust smell in the vehicle. The leak can develop in the muffler, exhaust pipe or even the manifold. As exhaust leaks into the engine compartment it will make its way into the vehicles cabin via the various vents systems in the vehicle. A persistent smell of exhaust in the cabin can be very dangerous and the car should be inspected immediately.

• Poor Door or Window Seals: Door and window seals can degrade over time and if they are failing, exhaust fumes can leak into the car. This can create a dangerous driving situation and the seals should be inspected and repaired immediately.

• Failing Catalytic Converter: If the smell resembles that of rotten eggs it is probably due to a failing catalytic converter. As the converter starts to fail, it no longer breaks down the sulfur created by the engine which leads to a strong rotten egg smell. Catalytic converters must be replaced, they cannot be repaired.

• Failing Heater Core: A smell of burning anti-free in the car is probably related to a leak in the heater core. The heater core itself may be cracked and leaking or a hose leading into or out of the heater core may be split and leaking. Bad seals within the heater core could also lead to this problem. In most cases a puddle of anti-freeze can be seen under the car after it is parked for a while.

While not life threatening, a big enough leak will drain the car of anti-freeze, causing the engine to run hot. This can lead to a number of more serious, and expensive repairs.

• Failing Oxygen Sensor: An oxygen sensor measures exactly how rich or lean the exhaust gases are when they leave the combustion chamber. The vehicle computer uses this data to adjust the amount of fuel entering the engine. If the sensor is dirty or failing it can send incorrect measurements. If the exhaust coming from the tailpipe smells like gasoline, the vehicle computer is sending too much gas into the fuel injectors and it is not burning it all off.

• Clogged Cabin Air Filter: This is a long shot but it does happen in some cases. A severely clogged cabin air filter could lead to air being pulled into the cabin through other vents which could lead to a slight smell of exhaust. If the smell of exhaust is severe, this is most likely not the culprit.