How to Keep Mice, Rats and Other Rodents Out of Your Car Engine
You may have bats in your belfry, but how about rats in your manifold, or mice in your motor?
It is a myth that small autos are powered by hamsters running on exercise wheels, but it is an unfortunate fact that rodents can live and create mayhem in engine compartments.
In fact, the damage done to vehicles by mice, rats, and their many cousins can be considerable.
Gnawing wires, ripping out insulation for nesting materials, or squirreling away caches of nuts and trash in car and truck engines can destroy some of man's most sophisticated transportation technology and cause significant financial loss.
This is especially true if you live in a rural area. You need your car to get to your job or to go shopping, but wood rats and other critters want it for their homes.
Some Techniques Work: For Some People, Some of the Time
Rodents are everywhere, and some are likely to invade your vehicle and do damage. They can find your car, decide it is a safe place to make a nest and a handy site to store food. If you can discourage them, you may win the battle.
There are dozens of techniques used to prevent mayhem by the destructive critters. Here are some successful measures rat damage victims have tried, especially in combination. Multiple lines of defense seem to work best.
Steps to take:
- Leave the hood up. Rodents are looking for a dark place to nest. This idea may help discourage nesting, but may not be practical in all situations.
- Hide your dog food, cat food, and birdseed. Dog food is the gold standard of rat society. Rats will stuff pounds and pounds of it into the air cleaner, glove compartment, or other empty spaces in your car.
- Remove or seal off rat hiding places near the car. Cut down nearby shrubbery and vines where they can hide. If you have a garage, block rat-sized entrances to the building, or spray them with substances or solutions that rats hate (see below).
- Block small entrances to the engine compartment. Some car owners place traps around the vehicle or on top of the wheels, since rats climb wheels to get into the engine. Some block engine openings with wire screen.
- Use electronic deterrent devices. Rodents can hear ultrasound, and it annoys them, at least for a while. Some learn to ignore it. Strobe lights like Mouse Blocker or Rid-a-Rat may work for longer periods, as they disrupt the darkness that rats prefer.
- Make your engine and its entrances smell bad, at least to rats. Motorists have had success with peppermint oil, powdered fox urine, used cat litter, cat hair, dog hair, Pine-Sol, Irish Spring soap, red pepper, and laundry dryer sheets. The people who make "Rataway" tell you to spray it on all the wires in the engine.
- Finally: use traps to remove the rats who get through. The old-fashioned snap traps still work. Glue traps work too but may torture the rat. Humane cage traps may work, but relocating the varmits can be a problem. Toxic baits do kill rats eventually, but are likely to also poison predators, including domestic animals.
Rodents Can Move in Quickly
Rural people know that a seldom used old car may be taken over by rodents, but they can also get excited about brand new cars. In less than 24 hours they can destroy much of the wiring.
Some plastic insulating material now being used in cars seems especially tasty to the tiny invaders. When mice chew the insulation off wires that connect batteries, alternators, or anything electric to anything else, they cause short circuits that result in costly restoration.
After the repairs, mice may go back to work and cause the same problem again, unless you take steps to prevent them.
Run! The Hood is open!
Mechanics See Engines Destroyed by Rodents
"Apparently they have nothing but time," says Rick LeDuc of Rick's Automotive Service in Mariposa, California. He has found elaborate nests in intake manifolds, and even litters of tiny pink mice inside air cleaners stuffed with bedding material.
In one of the more ambitious nests, he found part of a broom handle that had been dragged into the inner workings, as well as "a couple of pounds of dog food." In another instance, he said that only the wires coated with blue plastic insulation had been gnawed.
"They are supposedly color-blind, but sometimes they pick out one certain color of wire to chew," he says. Probably there's something about the taste or texture.
Several auto repair businesses report multiple incidents of rodent damage each month. The time of year doesn't seem to matter. Hoarding, nest building, and wire gnawing are year-round occupations.
Repair costs can be as high as $500 and sometimes much more. In at least one case, so much wiring damage was done that the car was not worth fixing.
Rural car owners sometimes come into a repair shop complaining that they "smell something burning.” Such an odor may come from smoldering grass or or pine needles tightly packed into a carefully fabricated nest, or from burning droppings, stashed food, pack-ratted items, or the deceased bodies of the actual culprits.
A lot of people are surprised to discover the source of their problems. Why are so many furry occupants living where they are not welcome? This is not their natural habitat. Are they planning to take over the planet by disabling our vehicles?
The real reason rodents seek a home under a hood is that it provides a dark, warm, secure place to hide.... at least until the ignition key is turned. The start-up of the car’s machinery can be deadly for the critters, and sometimes can cause serious consequences for the drivers as well.
An acorn, rolling into a crevice after a driver stepped on the gas pedal, can keep the throttle open. The driver of a late model Ford truck was taken for a wild ride on a winding country road, and severely damaged his brakes before he could shut off the power.
The wood rat culprit apparently abandoned ship before the adventure, but his hoard of nuts almost caused a real disaster. The truck required towing and lots of professional attention.
Anecdotal Results of Dozens of Strategies
Realistically, getting rid of rats may be a lengthy project, requiring multiple strategies. Every situation is different. As it happens, I have hundreds of anecdotes below, in over 270 comments sprinkled with suggestions, and you can read them all, or read my new article summarizing them, "Getting Rid of Rats or Mice in Your Vehicle: Reader Suggestions."
Briefly, I’ll summarize the results below.
- Remove rodent hiding-places next to your car. Cut down shrubbery and vines.
- Remove food sources near the car so the rats won’t be tempted to turn your car into a warehouse. Most notorious: dog food.
- Expose the motor to the light, so rats have no dark place to hide. Park with the hood up.
- Use traps. Baits risk poisoning pets or wild predators.
- Use strong-smelling substances. Compare readers’ results from using peppermint oil, powdered fox urine, used cat litter, cat hair, Pine-Sol, Irish Spring soap, red pepper, and laundry dryer sheets.
- Block small entrances to the engine compartment. Some place traps on top of the wheels, since rats climb wheels to get into the engine. Some block engine openings with wire screen or brillo pads.
- Use electronic deterrent devices. Some have had success with ultrasound devices, others swear by the strobe-light-emitting “mouse blocker.”
- Do not let the car sit unused. Drive it once in a while, see if rats have been doing mechanical or electrical work.
Collecting and Nesting Behavior of Wood Rats
John Muir, the famous Yosemite naturalist, called the wood rat (or pack rat) "a handsome, interesting animal".
In his detailed descriptions of Sierra flora and fauna, Muir also opined that "no rat or squirrel has so innocent a look, is so easily approached, or expresses such confidence in one's good intentions."
The comments of today's vehicle owners plagued by rodent motor damage are much less complimentary -- and are often unprintable. It may have been easier for the poetic naturalist to appreciate the animal, since he usually traveled on foot, rather than by SUV.
Wood rats are notorious for accessorizing their nests with things they collect, ranging from natural curiosities like bones, cones, and stones, to the tools, trash and treasures furnished by humans. Muir recorded incidents of rats stealing combs, nails, tin cups, eating utensils, and spectacles, which he supposed were used to strengthen rat nests.
Once inside an engine compartment, the rats see a mother lode of wonderful man-made objects, with wires and hoses and tubes connected to a spectacular variety of shiny metal and plastic components. To this assemblage, they will add their acorns, pine needles, hardware items, bottle caps, and whatever ornaments suit their eclectic decorating style.
Even before the era of motorized vehicles, settlers contended with these tiny terrors, doing their best to keep rats and mice out of their houses and barns.
Hard rock miners, however, actually encouraged rats to inhabit the mine tunnels, by saving crusts and crumbs of bread for them. The rats acted as a low-tech safety system. Being ultra-sensitive to tremors or quakes, they provided early warning of impending collapses or cave-ins. If rats suddenly went running for the exit, the mine workers were right behind them.
This may give us a clue that a deterrent that causes vibration or sound waves, may be a good choice.
One of the newest products addressing the wire-chewing problem is Honda Motor Tape. It is infused with pepper and perhaps some other deterrent and is used to wrap the wire harness. Early reports say it works well. It is not cheap, but costs much less than replacing an entire electrical system in your vehicle.
Honda Rodent Tape
.... Lurking, everywhere.
Some Less Serious Ways to Discourage Them
So are there other ways that pesky little wire nibblers and insulation grabbers be discouraged? Could a car be disguised with animal pelts, to make it look like a rat-eating predator?
Would a ground squirrel be tricked into thinking your car was a mountain lion or a giant badger with the help of a spectacular paint job? Or perhaps one of those big plastic owls could be stuck under the hood, and wired it up with a speaker playing annoying rap music.
Some people park their car over a bucket of mothballs, which is apparently repugnant to rat olfactory receptors.
The family dog or cat may help to keep mouselike pests away, though if the cat gets into an engine, it's bad for everyone -- usually worst for the cat.
There are also little buzzer things that are supposed to keep pets off the furniture. They might work.
The problem is not going away, so drivers might be wise to pay a little extra attention next time they notice an unfamiliar squeak in their vehicle.
They are out there.
Some of them know where you park your car.
Have you had this problem?
New Hub on Rats in Cars
My newer article (click here) summarizes the best car rat-proofing ideas contributed by readers in the 270+ comments below. Or read the comments and add your own ideas!