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My Car Smells Musty, What's Causing It?

by Eddie Carrara

Water leaks are like VooDoo for a mechanic, and very few will spend the time water testing the vehicle, crawling around inside the trunk, or under a dash with a flashlight looking for signs of water leaking into the car. Not only is it grunt work, but you also tend to get wet in the process. 

Trying to identify car smells can sometimes be baffling, but one thing is for sure, there is an answer. One of the most common car smells people complain about in vehicles is a musty or stale smell. The best air fresheners will not remove the smell because the source is still there. The common cause of this car odor is the air conditioner; the air conditioner removes moisture from the cabin air and drains out the evaporator's bottom.

The best way to prevent this car smell is to dry the evaporator before shutting off your car. Run the blower motor/fan without the air conditioner for approximately 2 minutes before shutting off your car; it will dry the evaporator fins, and most of the moisture will evaporate, leaving nothing to cause that odor.

The best way to eliminate the smell is to remove the evaporator and wash it with soap, water, and bleach. Some products will help eliminate the air conditioner's musty smell without removing the evaporator. Try 6oz. Wurth A/C & Heating System Treatment or einszett 961105 Klima Cleaner If you don't want to spend the money to remove and clean the evaporator. I have never used the foam, but I have used the 6oz. Wurth A/C & Heating System Treatment and have had excellent results.

Note: Vehicle water leaks from the windshield, windows, and exterior accessories, can also cause musty car smells, but the most common cause is the air conditioner.

My Car Has a Gasoline Smell

If your vehicle smells like gas or has even a faint fuel smell, you should have it looked at right away. Fuel smells are very dangerous and are a sign of fuel leaking or an opened vent in the fuel tank. Liquid fuel is not flammable, but the vapors are; that's why fuel smells are extremely dangerous. So if your car leaks gas or your car smells like gas, I recommend having it towed to the shop and have it looked at right away. Read more about this problem in another article I wrote, Gasoline Smell in Car.

Used Car Smells Like Cigarette Smoke

You just bought a used car, or you have just inherited a car from a smoker, and you want to remove the cigarette smell from the vehicle. There are products on the market that can reduce the smell but won't permanently remove it. You have to understand, it took years of smoking to permeate the vehicle, and there is no way to remove that car smell with an air freshener or spray.

A machine called an Ozonator removes car smells, but it can cost more than a hundred dollars, and there is still no guarantee it will remove the car odor. On some of our used vehicles that smelled like cigarette smoke, we used Auto Shocker ClO2 car interior odor eliminator; the residual smell was bleach, but this smell had dissipated within a few days airing out the vehicle. The cigarette smell was not gone completely, but it was 85% better. I think it was worth the money all day long.

Car Smells Like a Dead Animal

It's common to have animals running around inside your car while parked, especially near a wooded area, and it's cold outside. Animals like squirrels, chipmunks, mice, and rats look for warm places to build nests, raise their young, and hide their food—what better place than inside a warm, dry, comfy car.

Rodents will build a nest in the engine compartment and dash area, especially in the blower motor or ductwork. The first sign of a rodent living in your vehicle would be a noise coming from the heater fan motor or blower motor. If you turn the fan on inside your car and you hear a rumbling noise, it could be the first signs of a rodent starting to build a home in the fan motor.

Often, the animals will get trapped inside the motor and die; this is where the smell will come from, not to mention the smell of their urine and feces. The only way to get rid of this car odor is to remove the blower motor assembly and clean all the components with soap, water, and bleach. Bleach will also disinfect the area.

The above photo is fan or blower motor assemble we removed from a customers car filled with debris from a mouse. 

A squirrel was pretty busy getting ready for winter in the above photo. 

Melting Plastic Car Odor

A burning plastic smell will confuse every driver; it's an odor like melting wires. We get this complaint quite often and have an answer and a solution. 

Have you ever seen a plastic shopping bag floating around the highway or road? Well, now and then, a vehicle will drive over this bag, and the bag will stick to the hot exhaust and will melt, it's rare it would ever get hot enough to catch fire, but it will continue to melt and stink for weeks.

An easy fix is to have your mechanic remove the plastic bag from your exhaust system, and you'll be on your way. Remember to avoid those floating plastic bags on the road.

Your Car Smells Like Candy

Coolant has a sweet smell like candy. If your car is leaking coolant or antifreeze, you will notice the sweet aroma coming from your engine compartment or inside your vehicle if your heater core has failed. Antifreeze gets very hot and will start to steam, especially if it's spraying onto a hot engine or running down a hot radiator. If your car smells like candy, have it checked for a coolant leak right away.

This radiator is leaking at the bottom tank. This is a very common coolant leak for Honda Ridgeline, and Pilot. 

Rotten Egg Exhaust Smell

If your car has a smell like rotten eggs, it's an early warning sign your emission system is not working correctly; you might even encounter the check engine light being on if you have this car odor. If your car smells like rotten eggs, it's best to bring it to your mechanic and have it checked. The rotten egg smell is raw fuel that has not been appropriately burned and has turned to sulfur in the catalytic converter, which means your car is not running at optimum efficiency.

Above is an exhaust leak at the catalytic converter which can also cause a rotten egg smell.


I think I covered most of the smells you will encounter on your journeys; I didn't cover the smell of burning oil because I believe that car smell is unmistakable. If you see smoke coming from the engine compartment and you have to add oil every time you fill up your fuel tank, it's probably oil causing the smoke and smell.

If you have any other car odors, you can't figure out, or if there's something I forgot to mention, please leave a comment in the box below. You also have options to add pictures if you like. If you're ambitious, you could write a whole page about something you have encountered, and with my approval, I will make it part of my website :) So don't be shy. Step to the plate and write a comment, and I will get back to you as soon as possible.

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