It's cold out, you've just driven home from work for the weekend and parked the car, not intending to leave the house for several days. Flash forward to Monday; the car won't start. You look under the hood to find a nest made of trash and chewed electrical wires. A rat got into the engine compartment to stay warm after you got home on Friday, made a nest and damaged your engine. In cold weather, be vigilant about animals getting into your car's engine; this includes cats looking for a warm place to sleep.
Clear away any food, debris or trash cans from the area around the car. Rodents and pests are attracted to this as a food source. If they're not near the car in the first place, they won't know it's a warm place to be.
Open the hood when you get home to help the engine cool down faster and be less inviting. Only do this if the car is sheltered, or for a few hours, if weather permits, in un-sheltered conditions.
Fill a small net bag with mothballs and hang it under the hood of the car. The chemical smell deters most animals. Make sure it hangs away from any engine parts that become hot and away from any air intakes to avoid the smell getting into the passenger area of the car. For added safety, remove the bag while the car is being driven and replace it at a later time.
Set pest traps near or around the parking area to stop the animals before they make it to the car. Only do this if you have a particularly bad pest problem, otherwise, baited traps may attract a problem that otherwise didn't exist.
Sprinkle a pest deterrent around the car. These can be commercial products designed to deter pests, or hot chili pepper or cayenne pepper, which can be irritating to pests and keep them away.
Bang on the hood after you've left the car overnight. This will scare out any animal inside and avoid a messy engine clean up if the animal were to get caught up and killed.