Mice Are Living in Your Car Engine This Winter — And You Might Not Know It
This one catches people off guard every winter. You start your car on a cold January morning and smell something burning. Or you pop the hood and find shredded paper, leaves, and droppings packed around your engine block.
Mice. In your car.
It happens more often in Montreal than most people realize — and the damage can be expensive.
Why Mice Love Car Engines
When the temperature drops below -10°C, mice are desperate for warmth. A car engine that was running a few hours ago retains heat for a surprisingly long time. The engine bay is enclosed, dark, and warm — exactly what a mouse wants.
But it gets worse. Modern vehicles use soy-based wire insulation instead of the petroleum-based coatings used in older cars. Soy-based insulation is essentially food for rodents. They chew through it not just to nest, but because it tastes good to them.
Honda, Toyota, Kia, and Hyundai have all faced class-action discussions over soy-based wiring attracting rodents. This is not a fringe issue.
The Damage They Cause
Chewed Wiring
The most expensive problem. Mice chew through wiring harnesses that control everything from your headlights to your transmission. Repair costs:- Minor wire repair: $150-$300
- Wiring harness replacement: $500-$2,000+
- If they chew the main engine harness: $1,500-$4,000
Clogged Air Filters and Vents
Mice stuff nesting material — leaves, paper, insulation — into air intake systems and cabin air filters. This reduces engine performance and can cause your cabin to smell like a dumpster when you turn on the heat.Contamination
Mouse urine and droppings in the engine bay create a biohazard and a smell that lingers. If they get into the cabin air system, you are breathing contaminated air every time you drive.Fire Risk
Nesting material packed against hot exhaust components is a fire hazard. It is rare, but engine fires caused by rodent nests do happen.Signs Mice Are in Your Engine
- Droppings on top of the engine or along the firewall
- Shredded paper, leaves, or fabric packed into crevices
- Chew marks on wires or hoses
- A burning smell when you start the engine (nesting material on exhaust)
- Dashboard warning lights for electrical systems (result of chewed wires)
- Scratching sounds from under the hood when the car is parked
How to Prevent It
If You Park Outside
- Pop the hood when parked overnight. It sounds counterintuitive, but an open hood makes the engine bay less appealing — it is exposed and cold. Close it before driving.
- Remove food sources. Do not leave snacks, fast food wrappers, or pet food in the car.
- Use peppermint oil. Soak cotton balls in peppermint oil and place them in the engine bay. Mice dislike the smell. Replace weekly. This is a deterrent, not a solution, but it helps.
- Use rodent deterrent tape. Some manufacturers (Honda, Toyota) sell electrical tape infused with capsaicin (hot pepper). It deters chewing on treated wires.
- Clear vegetation around parking areas. Mice use tall grass, leaf piles, and debris as cover when approaching vehicles.
If You Park in a Garage
- Set traps in the garage. Snap traps along walls near where the car parks. This catches mice before they reach your vehicle.
- Seal the garage. Weatherstrip the garage door bottom. Seal gaps around pipes and utility penetrations. A mouse-proof garage is a mouse-proof car.
- Do not store bird seed, pet food, or garbage in the garage. These attract mice to exactly where your car is parked.
If the Car Sits Unused
Cars that sit for weeks — winter vehicles, recreational vehicles, cottages — are at highest risk. For stored vehicles:- Set multiple traps around the vehicle
- Place mothballs or peppermint sachets in the engine bay and cabin
- Start the vehicle weekly to disturb any nesting activity
- Cover the air intake with fine wire mesh (remove before driving)
- Use a rodent-repellent spray on wiring (available at auto parts stores)
What to Do If You Find Evidence
1. Inspect all visible wiring and hoses for chew marks. Pay attention to connections and harnesses. 2. Remove all nesting material carefully — wear gloves. Mouse droppings can carry hantavirus. 3. Check your cabin air filter. It is usually behind the glove box. Replace it if contaminated. 4. If you find chewed wires, do not attempt to drive. Have the vehicle towed or inspected by a mechanic. Damaged wiring can cause electrical shorts. 5. Clean and disinfect the engine bay and any contaminated cabin areas. 6. Address the mouse problem at the source — they are coming from somewhere nearby. If you are finding mice in your car, they are also in your house, garage, or building.
Frequently Asked Questions
Does car insurance cover mouse damage?
Comprehensive auto insurance typically covers rodent damage in Quebec. However, you will need to pay your deductible (usually $250-$500). If the repair cost is close to your deductible, it may not be worth filing a claim. Check with your insurer.Why do newer cars have more rodent problems than older ones?
Soy-based wire insulation, introduced for environmental reasons, is more attractive to rodents than the petroleum-based coatings used in older vehicles. This is a known issue across multiple manufacturers. Some owners install aftermarket wire loom or deterrent tape to protect vulnerable wiring.Got a pest problem?
Extermination DMP serves Montreal, the South Shore, Laval & the West Island — 24/7.
Call 438-879-5706