Rats in Car Engines and Garages: Prevention and Cleanup

Why garages draw rodents

A garage is sheltered, quiet at night, and often full of things rodents like: dog food bags, birdseed, grass seed, stored boxes, old furniture and clutter along the walls. Many Memphis-area garages also connect directly to the house, so a garage problem can become a kitchen problem.

The usual way in is the garage door. The rubber seal at the bottom wears out, especially at the corners, and leaves a gap. University of California guidance says a rat can squeeze under a door with a half-inch gap, and mice fit through openings slightly larger than a quarter inch.

Signs rodents are in your car

Pop the hood and look for:

• Droppings on the engine cover, battery or air filter housing
• Nesting material, like shredded insulation, leaves, paper or fabric
• Stored food, such as seeds or pet food kibble tucked into corners
• Chewed wires, hoses or the sound insulation on the underside of the hood

Inside the car, check the cabin air filter and the area under the seats. A musty or urine smell when the heater or AC runs can mean rodents nested in the air intake.

If you see chewed wiring, have a mechanic inspect the car before you take it far. Warning lights after a car sat for a while are a common clue.

Cleaning droppings out of an engine bay

Treat engine-bay droppings like any other: wear gloves, avoid stirring dust, and follow the CDC's wet cleanup method. Spray droppings and nesting material with disinfectant, let it soak, then wipe up with paper towels and bag everything. Do not use compressed air or a leaf blower, which spreads dust.

Replace the cabin air filter if rodents nested near it. A mechanic or detailer can clean areas that are hard to reach.

Sealing the garage

Most of the fix is on the building:

• Replace the bottom seal on the garage door, and add corner seals if gaps remain at the edges
• Seal the gap where the garage wall meets the slab
• Seal gaps around pipes, the water heater flue and any lines through the wall
• Fix or replace the weatherstripping on the side door
• Check the wall between the garage and the house for openings

University of California guidance recommends sealing gaps with metal, mesh or concrete rather than plastic, foam or wood. See rodent exclusion.

Removing the food and cover

Move pet food, birdseed and grass seed into metal or heavy plastic bins with tight lids. Keep boxes off the floor and a few inches out from the walls so you can see the base of the wall. Clear out old furniture, rags and cardboard that rodents use for nesting.

Start and move cars that sit for long periods now and then, and leave the hood up in a sealed garage if rodents have been a problem. A parked car in a garage with food on the shelves is an easy target.

Trapping in the garage

Snap traps along the walls where droppings show activity work well in garages. For rats, place traps along walls and behind objects; for mice, every few feet along the wall near activity. Put traps inside covered boxes if kids or pets use the garage.

Avoid bait in the garage if you have pets, since pets can be poisoned by bait or by eating a poisoned rodent, as University of California guidance warns. See best traps.

Outdoor parking and carports

Cars parked outside or under a carport are exposed too, especially near tree lines, creeks, dumpsters or bird feeders. Rodents climb into engine bays for warmth after the engine has run, and for shelter on cold nights.

If rats are active in your yard, park away from shrubs and woodpiles when you can, keep the area under the car clear, and pop the hood now and then to check for nesting material. Deal with the yard source first: trash, pet food, bird feeders and burrows. See rat burrow treatment.

Memphis garages and carports

Garages in newer subdivisions in Cordova, Bartlett, Arlington and DeSoto County are often where mice start. In older parts of Memphis, enclosed carports and detached garages behind 1950s homes often have gaps where newer walls meet older slabs. Warehouses and fleet yards around the airport and Lamar Avenue see the same problem at a larger scale. See mouse control and warehouse rodent control.