What Causes a Sour Smell Inside the Car?
4 Answers
Reasons for a sour smell inside the car: The air conditioning system has not been cleaned for a long time, leading to the accumulation of dirt and dust in the evaporator and air ducts, causing the air filter to mold: Seat covers, floor mats, etc., have not been replaced for a long time: Odors emitted by the original car decoration materials. In-car air pollution refers to poor air quality inside the car due to lack of ventilation, car body decoration, etc. The pollution sources mainly come from the car body itself and decorative materials, among which toxic substances such as formaldehyde, xylene, and benzene have the most severe consequences. When purchasing a car, choose a brand that has passed quality inspections. Wear gloves while driving or opt for environmentally friendly, high-quality seat covers. Additionally, try to open the windows frequently for ventilation while driving, and wash hands promptly after driving or exiting the car.
I've been driving for over a decade and have encountered sour smells in the car several times. The most common cause is mold in the air conditioning system. After using the AC in summer, condensation accumulates in the evaporator, mixing with dust, which eventually leads to mold and a sour smell that you notice when turning on the AC. Last time, I had it professionally cleaned—the technician flushed the entire air duct with disinfectant. It cost a bit but solved the problem completely. Another possible cause is leaving food scraps or spilled drinks in the car without timely cleaning, especially in corners where mold can develop, producing that sour, musty odor. A tip: always close the windows and doors when parking to prevent humid air from getting in. Regularly cleaning carpets and seat crevices can also help prevent such odors. In short, early detection and action are key—otherwise, it’s not just unpleasant but also bad for your health.
When I first bought my new car, I kept noticing a strange sour smell inside, which was really annoying. Later, I realized it was because I had left a damp towel in the trunk, and it had grown mold. I didn’t pay attention when using the air conditioner, and those tiny molds multiplied in the air vents. The solution was simple: first, I bought a car deodorizing spray from the supermarket and gave it a few sprays. If that didn’t work, I checked the cabin air filter and replaced it with a clean one, which usually eliminates most of the odor. Additionally, in some older cars, the sour smell might come from a leaking battery, in which case you’d need to visit a repair shop to check if the battery is aging. I’ve learned that developing good habits is crucial—like not leaving food in the car and cleaning up promptly. That experience taught me to always take a quick sniff before getting in the car. You don’t want your friends to awkwardly point out a weird smell when they sit inside—it’s uncomfortable and affects your image. Keeping the car clean is actually quite hassle-free.
When a sour smell appears in the car, I consider several key areas: first, a dirty cabin air filter breeding bacteria, which requires filter replacement; second, fluid leakage under the vehicle, such as battery acid or coolant evaporating inside, necessitating immediate inspection; third, interior materials like carpets absorbing moisture and molding, especially common during the rainy season. From a maintenance perspective, it's advisable to clean the air conditioning system every six months, using professional AC cleaning agents for a DIY approach. Additionally, avoid parking in damp areas to reduce mold risks. While the odor may seem minor, prolonged neglect could harm the respiratory system or corrode interior components—hardly worth the risk. Performing regular maintenance ensures safety and extends the vehicle's lifespan.
