A strong smell of mildew is one of the least inviting odors you can have in your car. Mildew is a type of fungus that thrives in damp environments and usually festers in your car's carpet or upholstery. The musty, earthy smell mildew produces is a clear sign that water has entered your vehicle and been allowed to sit for a good amount of time, fostering its growth. Ridding your vehicle of the smell requires some detective work and a whole lot of elbow grease.
Mildew grows in damp conditions, so where is the moisture coming from? Most often, water enters your vehicle through the weatherstripping around the windows and doors. Sunlight, age, and normal wear and tear all contribute to leaky weatherstripping, allowing water to enter your car and soak into the carpet and upholstery. If your vehicle is older and operated during harsh winters with road salt, also check the condition of the undercarriage where rust holes could be allowing water to enter the interior from underneath. Don't forget to check the trunk for water leaks as well. If everything checks out, and the interior is dry, suspect the air conditioning vents, where condensation can form and allow water to pool. If that is the case, run the heater at full blast as often as possible to thoroughly dry the vents and the odor will vanish with time.
Most commonly though, mildew forms in the carpet or upholstery. Once the source of the water leak has been repaired, you have two options: a professional cleaning at a detail shop or a thorough cleaning performed at home with the proper tools. Rent a professional vehicle carpet shampooer and purchase the recommended cleaning chemicals. Slowly work the shampooer over every square inch of carpet and upholstery and don't forget about the hard-to-reach areas under the seats. Repeat as many times as is necessary to thoroughly clean the interior.
An alternative method of cleaning the interior of your vehicle is with a Tornador, a professional detailing tool that sprays a high-pressure cleaning fog using compressed air. Of course this requires an air compressor, but the Tornador is much easier to use than the cumbersome shampooer. Simply fill the tool with a cleaning agent like Purple Power, Simple Green, or a dedicated upholstery cleaning liquid. Slowly spray the fog over every square inch of carpet and upholstery, and repeat as necessary until thoroughly clean. Then simply vacuum the interior with an ordinary household or shop vacuum.
After either cleaning technique, dry the interior as quickly as possible by running the heater at full blast or by driving the car on the highway with the windows down, preferably both. If possible, park the vehicle in full sun and leave the windows down for several hours. If the mildew smell persists, try using odor eliminators such as Febreze, Odoban, Clear the Air, or even ordinary household baking soda. If all else fails, you can mask the smell with air fresheners or remove and replace the carpeting or upholstery in the vehicle entirely.
