Do pests damage vehicles or machinery stored in garages?

This is one of the more honestly calibrated claims in this hub, and it's worth saying so plainly: a vehicle or piece of machinery that sits unused in a garage checks every box a rodent looks for. It's warm relative to the outdoors, it's sheltered from weather and predators, and — critically — it's undisturbed, which is the single biggest predictor of whether a rodent will commit to nesting somewhere. Extension wildlife-damage sources are consistent that stored equipment, seasonal vehicles, and idle machinery are classic nesting sites, right alongside attics and wall voids.

Once a rodent is established inside an engine bay, dashboard, or equipment housing, the same obligate gnawing behind every gnawing page in this hub takes over: incisors that grow continuously and must be worn down target whatever soft material is within reach. In a vehicle, that means wiring harnesses, sensor wiring, fuel and vacuum lines, and seat foam or insulation pulled for nesting material. None of it requires the vehicle to taste appealing or the rodent to be hunting water or food specifically — it only requires the material to be soft enough and the rodent to be undisturbed long enough to settle in.

A specific and widely repeated version of this story holds that automakers switched to soy-based bio-insulation on wiring harnesses and that this specific chemistry attracts rodents, effectively baiting them into vehicles. Class-action lawsuits pursuing exactly this theory against Honda and Toyota, filed between 2015 and 2020, were largely dismissed by courts citing insufficient evidence that soy-based wiring attracted rodents more than petroleum-based wiring. Honda stated it was not aware of any scientific evidence that rodents are attracted to automotive wiring because of soy-based content, and pointed out that rodents chewing vehicle wiring significantly predates the introduction of soy-based insulation by several decades. The damage itself is real; the specific villain in that version of the story isn't established.

Separately from rodents, a mud dauber wasp will sometimes plaster a mud nest inside an unused motor housing or equipment cavity over a season. This is a completely different mechanism — mud daubers don't chew anything and aren't after shelter from cold, they're building a nursery for their own eggs — and by the time you find the mud tube, the wasp has typically already moved on. It's cosmetic, static, and a simple thing to clean out; it isn't part of the wiring-damage story at all.