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The Hidden Damage of Mice in Your Engine (and How to Prevent It)

You’ve likely seen the blur of a mouse scurrying across the floor at some point or another. While you may worry about mice getting into your home, you should also worry about them getting into your vehicle’s engine compartment.

When searching for a place to make a nest, the must-haves on mice’s lists are relatively short, and your vehicle’s engine compartment checks all the boxes.

So how do you keep mice out of your vehicle’s engine compartment? Let’s look and see!

They Might Be Small, but Mice Can Deal Some Damage

While mice typically weigh anywhere from .02 lbs to .06 lbs, they can do an impressive amount of damage for their size. They’re not picky eaters, so they’ll gnaw through wiring, hoses, and belts looking for their next meal.

What’s even more frustrating is how quickly these pests can damage your vehicle.

Some drivers report experiencing severe issues from mice in just a single night. Between chewing through wires or hoses and their nests restricting airflow, these rodents can do thousands of dollars of damage to your vehicle in no time. And don’t think they’ll leave their insurance information behind to help pay for the damages they’ve caused.

In fact, last year, a mouse chewed through our Honda CRV wiper-fluid hose. This made use take more serious preventive action.

Why Are Mice Attracted to Your Vehicle?

Mice are typically attracted to any place with many tiny nooks and crannies that can keep them safe, and vehicles are full of them. If you’re not doing a great job keeping your vehicle cleaned out, it may attract them to it even more. A vehicle with half-eaten food or crumbs in the backseat from children snacking is an all-you-can-eat buffet for mice. 

You may not know it, but almost all vehicle manufacturers use soy-based insulation on wiring. The smells from the wiring can attract mice and cause them to nibble away at the wire insulation.

As the temperatures drop, the warmth of a car engine can attract mice to your vehicle. They’re looking to stay as warm as possible while they endure winter. A warm, dark, and tight-fitting space can feel like paradise to a mouse in freezing weather.

Pro Tip: Nobody wants a mouse in their house! The truth is Mice Love Your RV, Here are 7 Ways to Keep Them Out.

Mouse in car engine
A rodent infection in your engine can have big consequences!

Signs of a Mice Infestation in Your Engine Compartment

If you experience these symptoms, a rodent may have declared war on you and your vehicle. Let’s look at when it might be time to battle these pests!


Mice can produce up to 100 droppings in a day, which means they tend to leave a generous amount behind them wherever they’ve been. You should take mouse droppings very seriously.

Humans can contract diseases like hantavirus, hemorrhagic fever with renal syndrome, and lymphocytic choriomeningitis (LCM) when we come in contact with mouse droppings. You should always wear gloves and a mask when cleaning them up. If you find mouse droppings in or around your vehicle, it’s time to take action.

Check Engine Light

The check engine light on your dashboard can illuminate for various reasons. When mice build nests in the engine compartment, they can severely restrict the airflow to the engine. A lack of air will cause the engine light to come on and likely send you straight to a mechanic.

Ideally, a mechanic will remove the obstruction and fix the problem. However, we don’t live in an ideal world, and drivers aren’t always that lucky. Mice can chew through wires, air hoses, and belts that may also cause a check engine light to illuminate. 


Your engine requires all the components to work together in unison to function optimally. However, if a mouse chews through a hose or wires, it can throw these components out of sync. A driver may experience reduced power and performance, most notably stuttering or misfiring. 

Bad Smells

The ventilation system in a vehicle can provide an easy pathway for mice to access air filters and even insulation. These are both prime materials that rodents like to use to make nests.

As you can imagine, mice often leave droppings and urine behind when traveling through the ventilation system. When you crank on the heat or air conditioning to adjust the climate in your vehicle, you’re likely to notice the smell. Due to the difficulty of reaching some of the compartments, you’ll need a professional to help clear out debris.

Mouse sitting on top of car.
Mice are small and can easily squeeze into your engine.

How Do Mice Get Into Your Engine Compartment?

Mice are tiny and incredibly agile, which allows them to squeeze into even the smallest of spots. Unfortunately, vehicle engine compartments have massive gaps at the bottom for all systems to connect and communicate together. This provides them with a relatively easy path into the sensitive components of your vehicle.

Once they get into the engine compartment, it only takes chewing through a wire or squeezing their way into the ventilation system before you start to experience problems. While you’re not likely going to seal up your entire vehicle, there are a few things you can do to keep them at bay.

Pro Tip: We only want humans and cuddly pets in our RV! Use these 5 Tips To Keep Those Dang Bugs Out Of Your RV!

How to Keep Mice Out of Your Engine Compartment

The best way to avoid costly repairs due to mice is to keep them out of your engine. Here are a few things you can do to keep these critters out of your vehicle. Let’s get started!

Block Entrances

It can take tremendous effort, but steel wool and wire mesh are great options for blocking large gaps. Mice are nimble and can squeeze themselves through incredibly tight crevices. You must plug as many of these entrances as possible.

Clean Up Your Food

Don’t leave food in your car if you don’t want mice to come looking for food. Once mice find a food source, they’re likely to come back until it’s no longer available. Avoid keeping pet food, emergency food supplies, or garden seeds in your vehicle.

Parents with small children should frequently remove car seats to vacuum up crumbs and any remains of snacks. Under a car seat can be like hitting the jackpot for a mouse, and they’re not going to travel too far away from it.

Don’t Leave Your Vehicle Vacant

You want to consider where you’re parking your car. If you’re leaving your car parked for an extended period in a rural environment, there’s a good chance a mouse will eventually find your vehicle. While a mouse may find its way into your car, it’s not likely going to establish a nest if you’re regularly driving your vehicle.

If you’re planning to let your car sit for an extended time, park it in a garage if possible. While this doesn’t entirely reduce the risk, it makes it even more difficult for mice to get into your vehicle.

Use Repellants

Another fantastic way to keep mice out of your vehicle is to use products designed to repel them. Many of these repellents are spray-on products that won’t harm your vehicle or any of its components but have an odor that rodents hate.

Typically these chemicals smell like peppermint as this is a very strong smell they don’t like. Not only do these products keep mice away, but they also provide a delightful scent in your car and engine compartment.

You can also use electronic deterrents like flashing strobe lights or electronic buzzers that activate when they sense motion. These have varying levels of success, but many owners rave about them.

Like many mischievous beings, mice like to do their dirty work under cover of night. Leaving lights on or popping your hood to let light into the engine compartment can reduce the chances that they’ll find a dark spot to hide. If you ever visit a campground and see car hoods open or rope lights under vehicles and RVs, this is their attempt at preventing mice from damaging their vehicles and campers.

Mouse in hole
Get the mice out of your of your vehicle as soon as possible!

Getting Mice Out Of Your Engine Compartment

If you see signs that there are mice in your engine compartment, you’ll want to get them out of there as soon as possible. Wear gloves and a mask to protect yourself from any bacteria that may be in the nest or the droppings.

Dispose of the nest and do your best to clean out any debris from the mice in your engine compartment. If it’s rather dirty, you may need to give it a good cleaning. If you don’t know how to clean your engine, hire a professional to do the job for you. Keeping your engine clean helps reduce dirt and debris from attracting mice to the compartment.

Also, clean out your entire car and seal off any gaps where the mice could be entering your vehicle. Use sprays and other repellents to keep mice away from your vehicle and avoid letting it sit in one place for extended periods. The mice will eventually get the hint and leave, especially when the environment is no longer ideal for them to stay.

Are Mice Getting Into Your House, Too?

Mice can enter a house through small openings or cracks in the walls, floors, or foundations. They can also enter through gaps around windows, doors, and pipes.

Mice are also good climbers, so they can enter through vents or chimneys. They’re also known to gnaw through materials to gain entry. Properly sealing cracks and holes, keeping food stored in sealed containers and maintaining good sanitation practices can help prevent mice from entering a home.

Sounds daunting, doesn’t it?!

Keep Your Vehicle Mice Free

Dealing with mice in your vehicle can be rather frustrating and a bit gross. It takes consistency to get mice out of your vehicle and keep them away for good. While we generally encourage readers to be hospitable, you don’t want to create an environment that welcomes mice in your vehicle. By taking a few of the precautions we’ve shared today, you can help keep your vehicle mice free while cruising down the highways and on adventures.

Have you ever had to battle a mouse in a vehicle? Drop a comment below!

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  1. Dianna Urbigkit says:

    We had a mouse in our side boxes, so after removing everything and cleaning and then airing out, we use instant mashed potato! The mouse will feast on them! We also use them in our engine compartment when we sit! Mouse feasts on the potatoes, goes to find water since they get thirsty, problem solved! I don’t used-con or other chemical rat/mouse killer dur to my dogs. This works better than cheese and traps too!
    We sprinkle on the engine too….Not enough to block air flow…but enough to deter the mouse!

  2. Michael Matteson says:

    Are there any aerosol mice repellents that are recommended? Thanks for this usefule article.

  3. bruce n Steger says:

    I had the wiring under the intake manifold ($455 to repair) for the engines knock sensor eaten thru and my wife’s car air filter had a nest in it. After that I put screen material over the air intakes and epoxied a tray to a flat surface in the engine compartment that will not get water in that area. Mouse/rat poison is then put in the tray. I replace it once a year and notice a small amount was eaten each time. Chipmunk’s as well as squirrel’s can also do damage.

  4. Bob says:

    When I bought my 2001 Chevy Roadtrek class b 4 years ago I knew most of my camping would be out in the forest. So I bought a very small white LED bulb and attached it to a 30″ wire, and clipped the other end to the chassis battery. Dropped it down into the engine compartment. No switch is necessary as the Amp draw is infinitesimal. So is been on 24/7 for these 4 years and never a sign of mice.

  5. Bob says:

    @Bob, PS – I’ve never had a mouse inside either. No way in.

  6. Cheryl says:

    We have tried various deterrents but most do not work. I heard peppermint oil, dryer sheets, and Irish spring soap. I do keep electronic traps inside each vehicle. That gets them if they make it to the interior. Hoping people have more ideas. I heard one brand of hairspray works to keep out of the engine. Anyone heard of this?

  7. Michael Burkeens says:

    If they vehicle is setting for a while, just use moth balls. Not only will they stop mice, but also, snakes. Just put them in places that are easily seen. Don’t throw them in the air vents or your going to have a serious problem.

  8. Joy Gibson says:

    After having to pay just under $1,000 THREE times during two winter seasons to have wiring replaced that was chewed up by mice in my husband’s pickup and my car, your article definitely caught my attention. We live in the country, so there is very little to do to keep mice away. We are not wealthy people, so these situations really hurt the wallet! I like the idea of spraying peppermint extract on the engine compartment! We’ll definitely be trying that as a remedy. It has to be cheaper than the repairs!

  9. Sam says:

    I had a huge invasion of mice last spring while camping at Fort Peck Montana. Not kidding, first night woke up to at least 3 of them scurrying all over my van. Took a week of repellents and tons of sticky traps to rid them. They got under my floor, dash, engine compartment. But I won and yes, they did alot of property damage. The Mouse struggle is real

  10. Another Tip: If you keep Dry Dogfood in your garage, do so in sealed plastic containers off of the floor. Rodents of all sorts will take that food and store it their hidden spots, IE. your engine. I once found a possum in a customers Ferrari that did just that causing 20,ooo worth of damage.

  11. Greg says:

    Dryer fabric sheets work the best for keeping mice and rats out of the ancient compartments of cars and RVs

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