This is the evidence. Chewed cables. Bits of debris. Droppings. A rat has been spending time in your engine compartment.
Rats can cause tremendous damage, chewing through wiring, gnawing on hoses, plugging things up with debris.
The chances of trouble can increase if a car isn’t driven much, like during a pandemic when people are staying home.
Our car has hosted a rat, and we didn’t know until we took it for servicing. The service rep informed us that the mechanic had spotted gnaw marks on the battery wires and droppings around the engine bay. A notation on our bill made it official.
I responded by getting the engine compartment professionally cleaned (under $100). At the detailing shop, they told me that while they don’t get a rat cleanup every day, it is quite frequent.
After the cleanup, I didn’t want the rat to come back. So I looked up a pile of articles about rats and engine compartments. There are a lot of suggestions backed up by not much research. You can buy repellent sprays and sound emitters that are apparently unpleasant for rats, for example. But there’s skepticism about whether they work.
These are some of the approaches that make sense to me.
If rats have visited, do a thorough cleaning. The scent of rat urine can attract rats.
Turn on the engine occasionally. This might make the engine compartment less appealing. (But there’s also the stance that doing this could make things more appealing, because the compartment gets warmer.)
Don’t park your car near areas where rats like to hang out. If you have such an area at your house, get rid of it. It could be a pile of debris that gives rats a place to shelter. Or bins that are filled with food waste. Freeze your food waste and don’t put it out until collection day.
Shine light into the engine compartment, from the top or bottom or both. Rats apparently like to keep out of sight, and bright light makes that tougher. Some people think a strobe light would be more effective than just shining a light. (Though neighbours might not appreciate it.)
Honda sells a tape (not cheap) designed to discourage rodents from chewing on wiring. When I bought a roll, I was told that the mechanics had given it a taste: it’s very spicy. Wrap this tape around your wiring. Read the directions first.
Set traps around your car, particularly at the tires, which can provide a ladder into the engine compartment. I have not tried this. (Update: A concerned reader urges us to not use traps and poisons because they could harm children, along with cats, puppies and other animals.)
This suggestion comes from Toyota, shared via email as part of the company’s effort to help customers during the pandemic. I haven’t seen it mentioned elsewhere: sprinkle cedar mulch around the outside of your car. The scent can deter pest visits. I don’t know if it’ll work, but I’m going to try it out.
Update: A reader says the sound of human voices seems to be a repellent. So, play a radio near the engine compartment, maybe tuned to CBC, which has a lot of shows with talking.
