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Mice in the Car Engine: A $2,000 Surprise

Car won't start? Mice might have chewed the wires. Learn why rodents love soy-based wiring and how to keep them out of your engine bay.

August 01, 2025 1 min read

Mouse nest made of insulation on top of a car engine

It starts with a weird smell when you turn on the AC. Or maybe the "Check Engine" light flickers. You pop the hood, and there it is: a nest made of shredded napkins sitting right on top of your air filter.

Mice love cars. Modern cars use soy-based insulation on the wiring. To a mouse, your Honda isn't just a warm house; it's a snack.

Why it happens in winter

When you park your car after work, the engine stays warm for hours. If it's freezing outside, that engine block is a radiator for rodents. They crawl up the wheel wells and settle in.

They chew the wires to file their teeth. I've seen harnesses chewed through that cost $3,000 to replace. Insurance covers it sometimes, but it's a nightmare.

How to actually stop them

Standard traps don't work well in a driveway. Here is what I do for my own truck:

  1. Peppermint Oil: Rodents hate strong scents. Spray a peppermint solution on the firewalls (not on hot engine parts) or hang a specialized rodent repellent pouch under the hood.
  2. Pop the Hood: If you park in a garage, leave the hood open at night. It eliminates the "dark, cozy cave" feeling. Mice feel exposed and won't nest.
  3. Light it up: Put a cheap LED work light on the garage floor shining up into the engine bay. They hate light.