Tuesday, July 23, 2024 Detailed Auto Topics
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Any place that people live, we will also find rodents. They exist in many varieties and all have one thing in common. Rodents love to gnaw. When a rodent turns their eye to our automobiles, the results are expensive and inconvenient.

A big problem

Auto repair shops often see the damage that rodents cause. Many times the damage results in vehicles with a check engine light on and often a no-start condition. Repairing rodent damage can be expensive, sometimes costing thousands of dollars. One of the common targets for rodents is automotive wiring.

Rodents will often seek shelter under the hood of a vehicle. This provides shelter, safe from the elements and larger predators. Unfortunately, chewing on wires is their natural behavior and often results in damage.  Prevention can be difficult and repeat damage is very common if we cannot convince the intruders to move on.

Why do rodents get into our vehicles?

rodents like to nest under the hood and can cause a great deal of damage

Mice, rats and squirrels are all nesting rodents. With nesting rodents, a safe place to live is a high priority. These small creatures find the area under the hood of an automobile to be a great location. For them this area is easily accessible from under the vehicle, dark, warm and hidden.

Under the hood they find an abundance of material with which to build a nest. They often shred hood insulation and combine it with paper, leaves and other items they find. Vehicles that are not used every day are most inviting, but even our daily drivers are not immune. The problem is naturally worse in colder weather as food is less abundant and predators are searching harder for a meal.

Why do rodents eat an automobile’s wires?

Prevention is easier with an understanding of why rodents gnaw on our wires and other components. Contrary to the common belief they do not eat wiring for food. Instead, all rodents gnaw constantly to sharpen and keep the length of their teeth in check.

Unlike most mammals, a rodent’s teeth grow very rapidly throughout the life of the animal. A rat’s teeth can grow up to 2.8 MM in one week! In one year, the teeth grow almost five inches. Rodents gnaw things to wear the teeth down. If they do not wear away, soon they will outgrow the animal’s mouth.

The tooth of a rodent is a unique arrangement designed to stay razor-sharp. Very thick and hard enamel covers the front of the tooth. The rear of the tooth is softer dentin material. Dentin is similar to bone and wears much faster than the enamel on the front. This leaves a very sharp edge.

Experts rate a rat’s tooth enamel 5.5 on Moh’s hardness scale. Copper is a three and even iron rates as four. Cutting through a wiring harness is no challenge for such a hard tooth.

Injector harness severed by a rodent gnawing

Recently a vehicle came in with a check engine light. Rodents damaged wiring for the EVAP system. Evidence of their presence was clear. One week later the owner towed the vehicle in because it would not start. The uninvited guest returned and severed the wiring harness for the injectors. They route this harness under the intake manifold. The repair requires removal of the manifold and extensive rebuilding of the harness.

Spotting the signs of rodents

signs of a rodent under the hood

Prevention is best and vehicles driven less than daily are easy targets. Spotting the early-warning signs of a rodent may help prevent a costly repair. Any droppings under the hood of the vehicle, suggest activity. Pet food, leaves, twigs and other foreign materials, under the hood, are also signs that rodents may be present.

To help prevent rodents from attacking a vehicle, we can avoid parking under trees, around tall grass, wood piles and compose heaps.

chewed insulation and no fuel pressure, rodent damage

A rodent has chewed the insulation along the firewall of this truck. The vehicle would not start after sitting for a week. Testing revealed no fuel pressure and removing the fuel tank shows the fuel-pump harness has been chewed apart.

Fuel pump wiring damaged by a rodent

Parking the truck under an oak tree, for just a week, greatly contributed to the problem.  Rodents come from the tree and set up house under the vehicle.  While under this vehicle they eat through several critical components. Not shown is a partially severed fuel-line.

Preventing rodent damage

Folk remedies, like spreading hot-sauce under the hood are useless. Rodents have a large space in their mouths, from the front incisors to the rear molars. This space allows them to suck their cheeks in, blocking the mouth when they gnaw. Material being gnawed does not reach their tongue so is not likely that a bad taste will keep them from gnawing.

Rodents are also extremely adaptable. They are very suspicious of anything new in the environment, but quickly learn if it is a danger or not. Devices that produce sounds will not keep them at bay for very long.  Soon they realize this does not hurt them and they ignore it.

a cat may help keep rodents away from a vehicle

Predators are effective at keeping rodents away. A cat may not catch many mice but may keep them away from a vehicle.  Just the presence of a predator is often enough to convince rodents to look elsewhere for shelter.

Most rodents do not travel a great distance. They move about at night and try to stay under cover. Removing the things that provide shelter makes it far less likely they will stay around. Wood piles and tall grass, close to a vehicle, are an invitation.

Removing sources of food will also reduce the population. Pick up bird feeders and pet food at night. Keep garbage cans tightly covered. In multi-family housing, never park near a trash dumpster. Water is not as much of a problem. Rodents can go with almost no water to drink, gaining what they need from their food.

Moth balls are also effective at keeping rodents away. Placing several moth balls in old socks, and distributing them under the hood, may help keep the pest out. Replace these every few months as the chemicals evaporate over time. Also be careful where these are placed as they can be a fire-hazard, or corrode metal they contact.

Rodent resistant tape for repair of rodent damage

Being careful not to park under or near trees and keeping the area around the vehicle clear, will help prevent problems. Picking up all food in the area is also a great help.

If a vehicle needs repair, a rodent resistant tape is available. Taping the repaired areas with this material has proven effective, when combined with the above methods.

Finally, if a vehicle suffers extensive damage, a person's comprehensive auto insurance may also help pay for the repair. Contact your insurance agent and explain the problem to see is making a claim is practical.

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