While adding peppermint oil to my home grown rodent repellent apparatus yesterday I noticed a bit of "cotton" on the intake manifold (passenger side). I fished it out and discovered it contained seed hull fragments. I also think I see some droppings in the area in question, along with more debris. This is on a 2023 so everything is shiny and clean, making the debris very visible once you arrive at the correct viewing angle. It all looked recent, maybe coinciding with the arrival of colder weather here in the NE. I also don't use the truck everyday so that may contribute to the rodent residency. No wires appear to be chewed.

Anyway, check those engine compartments!

For the first time in 19 or 20 years of car ownership, I recently found (and smelled) a mouse nest -- on top of the HVAC filter where others have found them. It seems like this is becoming more common of a problem?

I'm still dealing with the smell -- my plan is to 3D print or cut from wire mesh a guard to cover the HVAC intake, but they were also in the intake air box pulling fabric from the front of the filter. I'm considering a few flashing LEDs in these spots.

I’ve had to do the wire mesh trick and it seems to have worked, at least there was no further evidence of mice.

Despite my dealer denying it, I’m pretty sure just one cold night parked outside the garage led a group of mice to use my 4Runner as a hotel.

Good to know. I'll check that filter too. Maybe this was the source of the "cotton."

Do flashing LED's work well?

Whatever repellent measures you try, first install a mesh screen (0.25 in grid or less) over the air intake. It’s an irregular shape. See photo below. Glue it down with a strong flexible adhesive.

Attached Images

 

I've had mice under the hood as well. I've found no nests nor damage, but have found kibble I keep out nearby for my feral cats stashed away in the rubber molding under the front of the hood on several occasions. Another favorite spot the mouse stashes kibble at is on the battery of my tractor, which is parked within a few feet of the food dish.

One thing that I did was to set a trail camera by the dish for the cats and have monitored it for a couple months. I've found that it's a typical small house mouse, who comes one to several times nightly to grab a piece of kibble and scampers off to stash it. There's been some close calls, as the cat has shown up less than two minutes later to eat and drink (I keep a 1.5 gallon heated dish next to the food).

Thanks to the suggestions I checked the cabin filter and engine filter. Both were negative.

But under the engine cover is a fibrous batting material (sound deadening?). Anyway a triangular shaped piece about 4"x5" was missing (chewed off). This batting is the same shade of white and same texture as the fluffed up nest that I found on the lower (aluminum) intake manifold. Again, no apparent wiring damage. A close call but I think crisis averted this time!

So add the engine cover insulation to the list of possible nesting materials. Oh, and there was some dried pee on the upper (plastic) intake manifold, along with some droppings too on the lower intake. I cleaned up everything I could see and added some peppermint oil to the engine cover insulation. Fingers crossed!

Peppermint oil will deter the mice and mask the smell. To eliminated the smell may take some more aggressive tactics such as A/C refresh kit: Amazon.com

Toyota also has an activated cabin filter that will absorb odors, or you can get baking soda cabin filters to absorb odors.

If you think mice are bad, I hope you never have to deal with a wasp nest. I had a colony of wasps set up home in my RAV4 last summer. Wasps! Help! | Toyota RAV4 Forums

Could not find the nest so using wasp spay would have been worthless. They do make an insect fumigator, but those seldom work on big critters like a wasp. Had to take the RAV4 in for oil change in the middle of this and dealer had to deal with them too. He couldn't find the nest either.

Final solution was to park the car far away for a few hours during the day. Wasps go out to forage during the day, then return to the nest at night. While the wasps forage, drive home and the wasps are gone.

What do you mean by the HVAC filter? The cabin air filter in the glovebox? I pulled it just to check, but do not see anyway for mice to get into it. I assume the intake is under the grill under the windshield wipers?

That’s correct.

We will add this in our to-do list.

Thank you. However, again, I cannot see any way for mice to get into the duct and nest atop the filter media, either from the outside (the grill openings under the wipers are too narrow for entry) or under the hood. Let alone a place to place the screen shown above. Were there changes in the ductwork of the 5th generation somewhere in the years? I have an '18.

Mice can get through an incredibly small gap, as little as 1/8". Stop thinking in man size terms; there are numerous places for the mice to get in.

That is why screens seldom work. Better to use mouse repellent such as peppermint oil or moth balls.

I've filled a few 2" square canvas pouches with cat hair (steady home supply) and left near front cowl and under both front weather tech floor mats. No issues with my new 2013... not that I had issues previously.