Rats and Mice in the Garage or Car Engine: What to Do

Rats and mice move into garages because garages hold everything they want: shelter, stored seed and pet food, trash carts and clutter to nest in. When it gets cold, a car that just came home has a warm engine bay, and rodents crawl in to nest and sometimes chew wiring. The fix is to remove the food, trap along the walls, seal the garage door and slab edges, and check the engine regularly.

Detached garages on Cleveland's narrow lots and attached garages in postwar suburbs both see this. Here is how to deal with it.

Signs rodents are in the garage

Droppings along walls, on shelves and near stored food
Chewed bags of bird seed, grass seed, dog food or fertilizer
Shredded paper, insulation or fabric collected in a corner, box or drawer
Burrows along the outside of the slab, especially on detached garages
A gap at the bottom corner of the garage door with grease marks around it
Leaves, twigs or nesting material on top of the engine or in the air filter box

Norway rat droppings are about three quarters of an inch long. Mouse droppings are an eighth to a quarter inch. See our guides to rat droppings and mouse droppings.

Why rodents go into car engines

A car that was just used stays warm for hours, and the engine bay is sheltered. Mice and rats climb in through the wheel wells or from below. Some build nests on top of the engine or in the cabin air filter housing. Rodents gnaw constantly to keep their teeth worn down, and wiring, hoses and insulation are in easy reach.

Signs of trouble include a nest under the hood, droppings on the engine cover, a burning smell when the engine warms up, warning lights or a car that will not start. If you find chewed wires, have a mechanic check the car before taking it far.

Clear out what draws them

Store bird seed, grass seed and pet food in metal cans with tight lids. Rodents chew through plastic and paper.
Keep trash carts closed and, if they live in the garage, clean.
Break down cardboard boxes and get them out of the garage.
Move stored items off the floor onto metal shelving, and keep a gap between storage and walls so you can see the edges.
Remove old fabric, rags and furniture cushions that make good nesting material.

Trap and seal the garage

Set snap traps along the garage walls, behind stored items and near any gap at the door. Rat traps for rats, mouse traps for mice. Put them in boxes or stations if kids or pets use the garage.

Then seal:

The garage door bottom seal. Replace a worn one. If the slab has settled, the door may need adjusting or a seal with a metal retainer.
The gap where the slab meets the wall, especially on detached garages
Holes around wires and pipes
Side doors, with a sweep if daylight shows underneath
Burrows along the outside of the slab, treated and then filled, with hardware cloth or gravel along the edge

The CDC recommends hardware cloth, metal sheeting or cement for larger holes.

Want a technician to look at it?

Your call goes to an independent rodent control provider serving Cleveland and Cuyahoga County. Describe what you are seeing and ask for a written quote before any work starts.

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Protect the car

Pop the hood every week or two in cold weather and look for nesting material or droppings.
Use cars regularly. A car that sits all winter is more likely to become a nest.
Keep the garage door closed at night.
Set traps near the car, out of reach of pets.
If you store a car for the season, check the air intake and exhaust for nests before starting it.

Some drivers wrap wiring in rodent-resistant tape or use repellent sprays. Evidence for repellents is limited. See do rodent repellents work.

Detached and attached garages are different jobs

Cleveland and its older suburbs have a lot of detached garages at the back of the lot, often next to an alley or a neighbor's garage. Many sit on a simple slab with no foundation wall, so rats dig under the edge. These garages need burrow treatment and slab-edge protection more than anything.

Attached garages, common in postwar suburbs like Parma, Maple Heights and Westlake, have a different weak spot: the door into the house. A worn sweep or a gap around that door lets mice into the kitchen or basement. Seal the door into the house as carefully as the big garage door.

When to call for help

If rats are burrowing under the slab, if you keep catching mice after sealing, or if rodents are moving from the garage into the house, call a technician. An attached garage gives rodents a short trip into the kitchen. See basement and garage rodent control.

Frequently asked questions

Will car insurance cover rodent wire damage?

Some comprehensive policies do and some do not. Check your policy or ask your agent.

Do mothballs keep rodents out of cars?

Mothballs are pesticides that must be used only as the label directs, and using them in a car or engine bay is not what they are labeled for. Traps and sealing the garage are the better route.

Why do I see rats in my detached garage but not my house?

Detached garages often have no foundation wall, just a slab, and rats burrow underneath. Treat the burrows and seal the slab edge before they move closer to the house.

How do I keep mice out of a garage door?

Replace the bottom seal, and if the slab has settled, adjust the door or use a seal with a metal retainer. Mice need only a gap about a quarter inch high.

Get a rodent technician on the phone

Free to call. You are connected with an independent provider serving Cleveland and the Cuyahoga County suburbs. Same-day appointments are often available.