Rat flap in a Subaru?

Ever since I bought this car new from the dealership, I have been trying to find out how the mice get into it. All the time, a lot of mice over the years. None of my other vehicles have this issue.

Well today I found out why. I had set a trap Sunday for the latest member of the Mickey Mouse Club. I forgot to check it Monday and it was 100F. Tue morning I opened a door and OMG. I opened the trunk and found the dead mouse in the trap with assorted flies and maggots. I took the trap and mouse up to the drainage canal and threw it in, not reusing that trap again.

Then I began the disassembly of the trunk, getting every thing out for a good hose down. I pulled out all the trim and panels from the trunk again, done this before looking for the entrance point. Again I searched. But this time I noticed something. I had always assumed it was a box for the side markers and never paid attention to it. But this time I noticed there were no wires going to it.

It appears to be a vent to let air out of the vehicle, one on each side. It’s about 7x9" and has a bunch of panels about 1x2, or so I thought they were panels, they are flaps. They hinge at the top. They are little pet doors for vermin. The other side is behind the bumper cover and there is a little shelf for them to sit on as they nudge the flap open.

After vacuuming out all the mouse poop, pecan hulls, acorn hulls, maple wings and other assorted seed pods and scrubbing down all the little urine trails and removing all the nests they made from the sound insulation used between the panels, I Ozark Engineered a solution to keep them out.

The proper way would be to remove the vents and fix them out of the car, but noooo. Subaru cleverly sandwiched them between the bumper cover and the inner panel. You have to remove the bumper cover, and that means removing the wheels, the mud flaps and the inner fender wells and getting the special tool that releases the bumper cover fasteners. So I fixed it in place with some 1/4" hardware cloth and some wood shims.

BTW, Home Depot hides the hardware cloth and none of the employees know what hardware cloth is, so today was also a training day for me as well, training the HD employees.


I don’t have much experience but hate those little buggers. I first thought the 1/4 “ screen would be a little big and might need to get the smaller stuff. Most people call it screen though and not hardware cloth so that might have been part of the problem. Looks good though with nice square corners. Hope those little buggers dont get caught between the flaps and screen though so check often for a while.

Reminded me it’s time for my monthly rodent spray treatment around the house.

A mouse can get through 1/2" hardware cloth but not through 1/4". I have a roll of 1/2" laying around and I’m sure I had a small roll of 1/4", but you know how it goes. Can’t find it when I need it and it will be in my way when I don’t.

You did a good job, Keith. I did something similar with the engine air intake of my old Outback after I discovered a mouse nest inside the air filter enclosure.

In addition to spraying rodent repellant in my current car’s wheelwells and in some crevices under the hood, I place at least 6 mousetraps–baited with peanut butter–around the garage. So far, no rodents in the new car, but I do catch at least one in a trap every few weeks.

I did find one once when changing the air filter element. BTW, mix a little molassas with the peanut butter. I have set a trap in the kitchen with this once, closed the cabinet door and before I got out of the kitchen, I heard it snap. It’s my go to now.

I have the sticky pads around the garage. Never caught a mouse in them though but some insects that try to crawl through. A few years ago I chased one out one night though. I’ve got a couple o& those electronic things too that I doughy do much. I try to keep the garage doors sealed pretty good though with that bottom track glued to the floor, ehatever it’s called, and the side weather strips. I noticed a little gnawing a couple years ago so installed those metal rodent guards on the garage door corners. They go up about 8 inches from the ground so the critters can’t chew through them. I’ve got three doors though so a little effort.

I was trying to figure out the wood shims at 1st, but saw the picture and it was a duhh moment… lol

Looks good Keith and if it works it works…

I had to do the same thing to the intake snorkel under the front valence. They would climb the fender and go down that snorkel tube to the filter box. Once they pushed past the filter element, they were in the ducts. A screen over the inlet stopped that. I like your construction, much more refined than mine.

Wouldn’t they be in the throttle body then? Presuming modern fuel injected car.

I don’t recall where I heard this, but recently someone had a problem with acorns in the throat of their carurettor. I could never understand how a rodent could get to that spot. But maybe your theory that the air filter is flexible enough they can just push themselves under the air filter element.

… lol … nothing more needs to be said on that topic except for a good chuckle … lol … in the store staff’s defense, referring to that product as “hardware cloth” is a little misleading.

It’s hard to understand why a car company wouldn’t anticipate this sort of potential problem and design their new cars passenger compartments and trunks to be completely mouse-impenetrable. For those vents, which are a functionally necessary part, easy enough during the manufacturing process for them to do what you did.

No, this is not the engine intake. It’s the fresh air intake for the passenger cabin.

Ok, thanks for clarification. We still need an explanation for the story about the acorns found in the throat of the carb though …lol …the big-donut shaped engine air filter on my truck just seems too stiff for a mouse to be able to push under.

Ya got me thinking rodents now. Isn’t the intake the grill at the base of the windshield?

The hvac fresh air source is a vent/grid near the bottom of the windshield on my Corolla, but on my truck, different path. Neither has openings big enough for a mouse to get through though.

The flapper assy is for depressurization so slamming door does not annoy passengers with sensitive inner ears. Or to help integrity of window door seals. The assy is mounted in trunk sheet metal and is behind the plastic bumper cover. Obviously there is enough of a gap from plastic to metal panels that rats can sneak in.

I only recently found out about those vents, you can see them when the rear bumper covers are removed.

The grille is a leaf filter. Look through the grille or better yet, up through the cabin filter and you’ll see the snorkel that feeds the fresh air intake. It sticks up from the cowl so water can flow around and down the cowl and not into the air intake. Mice can climb the fender/cowl, go under that grille and into the fresh air intake. Designs vary so likely variations on the way it is applied but the basic inlet exists on all. Some may have screens already. None of mine did so I add them.

Monthly rodent spray? Where do you live? I have lived 8o+ uears in Western NY, 70 of it in suburban Buffalo and 53 years of hundreds of yards of open field behind my house and never once a eodent in my car. Basement and attic every fall but never in the car. peat nutter in plastic snap traps work well to eliminate them and you don’t have to touch the mouse.

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I’ll have to look closer. There is window screen under the grill in the Pontiac anyway. May have to take a trip to the hardware store.

Only once 40 years ago did I have anything in/on the car. Car was parked in the garage for a couple weeks while we were on vacation. Found a nest of babies in the air cleaner. I’ve never had them in the house but did see them in the back yard when there was a corn field. Ran over them with the mower. The snake too.

Yeah, cars I use regularly seldom have issues. Anything parked is fair game for the mice. They get into everything- cars, boats, trailers. We have woods all around and mow about 2 acres around the house. Maybe because I don’t use any pesticides or other lawn treatments. We have abundance of wildlife and don’t want to harm the hawks and owls. Late fall, mice start looking for anyplace warm and can squeeze through a hole the size of a dime practically. They can get past the garage door corners so I put out snap traps starting in October. If I catch them right when they get into the garage, I don’t have issues. Usually quite a few in the early fall and then nothing. They come in waves followed by the predators; hawks, bobcats etc. Then for a year or so, they are less prevalent until their populations rebound. I had a hawk hunting from the roof of my house- he was very welcome here and watched him catch mice and moles right in the front yard.

My grille has a screen on the inside surface too but it is not protecting the air inlet. I wouldn’t get too concerned if you don’t have problems.

The label on the package says “Hardware Cloth”. It does call it anything else. I have never heard it called anything else until the second employee at HD asked if I mean “Chicken Wire”. It was located outside under the roof with no lighting, quite dark in that area, next to the chicken wire. I don’t see how calling it Hardware cloth is misleading.

For many years, when I have asked people about the mouse problem, every one points to the cabin intake vent. I have had mice get into vehicles through that, but they never got any further than the squirrel cage. That is where they died as soon as the blower came on and I knew instantly what was going on, the blower makes a heck of a racket. But I did remove the cowl to see if they had gotten in that way. I have put hardware cloth over the vent opening to keep mice out of the blower motor in the past, but all the other vehicles I’ve had used a snorkel type vent, Subaru does not and there is no easy way to cover the vent. I am thinking about cutting a piece of hardware cloth to fit on top of the cabin air filter next time I change it.

I have also found seeds, nuts and nesting materials in the air cleaners of some vehicles in the past. They never got past the filter though. Never actually found a mouse there either, just the evidence of their visit.

So three different types of rodent issues here, mine was with the rear vents, but clearly I have experienced all three in the past as many of you have as well. It’s just I don’t see the other two as a problem.