Keep Mice Out Of The Cabin Filter!

When I had my windshield replaced this year I saw how the technician had to remove the wipers and plastic cowling to accomplish the job. This exposed the large oval cutout which is the air intake port of the HVAC. Underneath it is the cabin filter and no wonder mice are attracted to it, it’s a nice little comfy nesting area for them.



So I decided to cover it with some screen to exclude them, or at least make it more difficult for them. And to keep out the leaves and pine needles that sometimes get sucked in.

First, you have to remove the windshield wiper arms. Start with the driver side. Pop off the plastic caps with a good grip of your fingers. Straight out. No need for any tool. Remove the 14mm nut with a socket wrench.



Then work the wiper arm off the toothed shaft. It’s kind of a pain but you have to wiggle and lift for a while to work it off. Repeat on the passenger side.



Lift the hood and remove the two push-pins, one on each side of the plastic cowl under the windshield. Like the ones one radiator cover. Push down the center with your finger and gently pull the whole thing out of the hole. Pop the center pin up to prepare it to re-install later.


Remove the small plastic end pieces at each lower end of the windshield. There are some clips on the lower edge and a pressure fit wedge at the top. Gently use a plastic trim tool to pry it up and out. Take your time.



The plastic cowling is held down with plastic clips. Push them toward the rear of the vehicle to release them. Pull the cowling toward you, away from the windshield, and set aside.



Now you can see the air intake opening in the passenger side. Clean it up as needed with a vacuum and isopropyl alcohol.



I took a piece of cardboard, about 10 x 4 inches, repeatedly trimmed it so it would fit snuggly over that hole, to make a template. When satisfied with the fit I used the template to cut a piece of enameled gutter screen to match it.



Laying it on top of the hole I temporarily taped it down snug in a few places and spot tacked it down around the perimeter with my favorite E6000 clear adhesive. After it cured I removed the tape and tacked those edges with more adhesive.



Let it dry, test your HVAC, reassemble, raise your favorite beverage, and toast to the resistance!

 

Excellent thread and timely too.

This looks like a worthwhile mod having just experienced a chewed up cabin filter last week.

Gutter screen is a great choice, it’s fairly robust. I was thinking of doing this but maybe using short self taping screws rather than glue. Pros and cons to either method.

Thanks

 

Yeah, not only are mice a nuisance their waste spreads disease. Like hantavirus, which can be fatal.

Screws and washers would be a good choice. The ultimate would be a metal frame screwed on top and around the screen to snuggly press fit it around the opening.

 

Funny thing? Last week after we discovered the cabin filter damage on both my 4Runner and the wife’s Sequoia, I cleaned it up, put the peppermint oil in the engine bays, set several mouse traps in the garage and have not seen any further evidence of mice.

Traps have not caught any mice.

I don’t know if the mouse didn’t find what it was looking for (food) or if the peppermint oil in the cars and garage is keeping them away?

 

Nice work. Glad the wiper arms came off easy, they can be a pain sometimes. Is your truck stored outside?

 

Mine is garaged most of the time at home. But it gets parked in the woods a lot during hiking and backpack trips.

 

You could have been a little more detailed..... LOL - Excellent job and thanks for taking the time to post some great info! So far my 4runner has escaped the varmints but in my own back yard they attacked my Yamaha Rhino eating up the injection harness - thank God in my former life I was in auto electric. Then in Tennessee they did severe damage to my toy-hauler generator - that was a nightmare to repair totally off-grid. I so appreciate people's efforts in sharing their knowledge on this forum - please keep it up. Sandbuster

 

nice write up!!! Now this is a mod worth doing soon!

 

Without a specialised puller these can indeed be hard to get off. One trick I found is to take a medium sized pair of channel lock pliers, and adjust the jaws accordingly so that you can catch the back of the wiper arm with the tip if the upper jaw, while the tip of the lower jaw rests against the center of the stud. Then slight pressure should pop it right off.

 

That’s a good tip, thanks.

 

Excellent mod and write-up. Thank you. I am going to this to both of my 4Runner's.
I think I am going to use stainless steel mesh screening and stainless screws (rust control) as I take my 4Runner on the beach.

$5 1 PC 11”X14” (28cmX36cm) Wire Mesh 5 Mesh, Sturdy Metal Mesh Sheets for DIY Projects 304 Stainless Steel No Rust Mesh Screen

https://www.amazon.com/28cmX36cm-St...=Mesh+&+Wire+Cloth,industrial,178&sr=1-6&th=1

 

I did the plastic air intake grill next to the hood/windshield ... GM on my old vehicles have a alum insect screen .. GM factory does the install to remove tree/crap.. now I put on my runner I put a insect screen black fiberglass on top of the air exterior grill.. now my air filter is not a load of a mess.. then I pulled that plastic air grill and I put a steel rat wire 1/2 inch to stop the rodents into the interior vehicle ...
I used a silicone sealer to lock up the screen and metal rat wire...I had no issues .. I also spray peppermint in the engine area ..
rodents like soy wire insulation new vehicles ......................old GM insulation ,,, rodents do not have soy .... no rodent chewing on my old GM vehicles.

 

Yeah but 9 out of 10 rodents agree, Toyotas taste better!

 

That sounds like a good technique to keep out vermin. Mice can squeeze through a hole the diameter of a dime. Rats, a nickel.
Do you have any photos of your install to post?

 

I don't have any pictures ... I did it 4 yrs ago and its working ...
what I can do is create the pictures in the warm temps to remove that soft plastic and I will clean , under the plastic vent air input....
also when I was looking up runner in 2015 ... the HVAC fan was damaged and the air filter was totally loaded with crap...then the motor has a damage ..

 

Did you ever complete this project using the ss mesh?

 

When I took my 4Runner in for its 5000 mile service, this is what they found. My 4Runner was in the garage and never parked outside. Toyota installed the wire mesh and replaced the filter. They also installed a flashing led light under the hood that is supposed to keep the mice away.

 

Tundras are plagued with the same issue except there are multiple places where they can get in that need mesh to stop them.

 

Yes I did. Pretty easy to do. The stainless screen is easy to work with. I decided to not use any screws (panicked when I thought about drilling into the truck), so I just cleaned the area really well with acetone and put down a bead of high quality marine silicon around the perimeter and set the wire mesh in place. So far no rust!

 

Thanks for the response. The thought of using screws would make me nervous also...sounds like you found a good solution. Plus, it could be removed later if needed without leaving any holes.

I may follow your method for my 4R.

Thanks @ElectroBoy for the idea and thread!

 

Good advice and great tips! Thanks

 

Yep, those little bastards. I first dealt with this on my 2006 4runner and now those revolting creatures from the pit of hell have defiled my 1 year new 2022. Took it for a drive last week and that putrid urine smell came wafting out of the A/C. But my fault I suppose as I assumed Toyota would have figured out the monumental screen-the-damn-cabin-air-intake engineering feat during the intervening 14 years. I guess not. And I didn't really want to tear apart a new vehicle speculatively to do mouse abatement. But here we are.

In my 2006 I used fairly heavy gauge expanded metal sheet. Considerably more substantial than the gutter screen referenced above. However the gutter screen has a much smaller open aperture which virtually guarantees those little bastards won't contort through. In the 2006 I also had to screen off far right and left drain areas of the cowl area as a first line of defense. Don't want a nest ending up anywhere in there. And then I placed mesh over the entire intake tunnel vs. set inside of the intake trough. Motivation being I didn't want to leave any sort of container area which might seem attractive as a nest location. Never had a problem with cabin air intake nor engine air filter after screening the latter at the same time to avoid a worse problem. I did have the little bastards get into the headliner of the 2006 when I wasn't driving over the winter trying to avoid road salt corrosion. And a year ago the 2006 failed inspection due to excessive frame rot anyway. Sometimes you just can't win.

 

Good post! Mice hate peppermint oil. Spray it liberally throughout engine bay, cabin interior and on the cabin air filter. They will run.

https://www.youtube.com/watch?v=wNaNGH_hnEE

 

Yea I already had a bottle of peppermint oil in the Amazon pipe arriving here on Sunday. The replacement cabin filters from Amazon on Saturday. Who needs to drive anymore? I plan to have at the screen install tomorrow as well. I've also heard from neighbors repellent packs hung in the engine compartment, etc.. seem to help. I believe all 4runners have a sunroof drain opening through the left body rear cargo area whether the vehicle is equipped with a sunroof or not. And the 5th gen 4runners appear to have a vent in this area as well as the right hand side. So those may be location requiring some sort of additional screening to prevent entry. Once these little bastards get into a headliner the mess they make is simply unbelievable.

[EDIT] Forgot to mention the wiper arms of my 2022 came off with a very modest amount of wiggling by hand. No need for tools sans the 14mm socket to remove the nut. I did use a thin blade spudger tool to remove the bolt caps. Part because these vehicles GREW in size since my 2006 and getting at the passenger side wiper base was a real (and literal) stretch. I wonder how replacement windshield installers manage to get the job done without some sort of scaffolding arrangement.

 

You can easily & cheaply make your own peppermint spray. I use it for aphids in the garden and spiders around the house.

Recipe:
Quart of water
10-20 drops of peppermint essential oil
1 teaspoon castille soap(I use Dr. Bronners peppermint)
Shake vigorously before & during use.

The soap doesn't need to be mint scented. Its only for emulsification and adhesion. Other Non-scented soaps or dish detergent are just fine. Wear gloves or don't touch your face even after several hand washes after handling mint oil. Its potent.

I would use caution spraying this or commercial sprays on any rubber seals or exposed wiring to prevent artificial aging. In camp, you can use this around tires as an extra measure. No lasting harm to most environs.

You can also use the following recipe for exposed skin to lessen mosquito load around you in camp.

1 oz Apricot Oil
5 Drops Orange or Grapefruit Oil(just for scent balancing, not actually needed)
7 Drops Lemongrass Oil
10 Drops Peppermint Oil
Put into a glass dropper bottle. Stores for 3-5 months. A few drops rubbed on arms and below knees will do. After applying, use oily hands to wipe on chest/back of neck. Avoid face.

 

That's actually where I was headed after realizing although pure peppermint oil is expensive ($3~4) per oz., the commercial mice repellents have under a 1% oil component. The sprays with actual success reports appear to be about 5% oil with the balance a water/soap mixture. The residual soap will render the oil film susceptible to wash off by water which could be a pro/con depending on situation. Using 70% isopropyl alcohol as a carrier would circumvent this concern. But I haven't been able to experiment yet w/r/t ratio and repellent effectiveness and whatever I use will most likely be far beyond the minimum concentration required.

 

@uhmgawa

No clue on the formulation of commercial repellants. The percent by volume they report or list could vary widely from what is available to consumers. It matters how pure/strong the oil is in the first place. There are multiple extraction methods used to manufacture fragrant oils. I use Now brand oils. They tend to be on the stronger side from my experience. Other brands I've tried have muted scents and some have off notes that to me suggest they're using carriers or adulterants as diluting agents. That said, 1.6 ounces of essential oil per quart(thats 5% by volume) seems excessive. Not to mention noxious to anyone that would have to remain in any sort of proximity to that. My eyes would not be able to take that pouring through my air vents. Don't imagine many others could either.

As for application. The method I use above would be safer for what is intended here. Which is keeping rodentia from nesting in the 4R fresh air intake. Applying excessive essential oils to plastics, rubber, and soy based wiring is a bad idea. Not sure of its longterm affect on paint either. And yes, ISO is a great carrier, as is lightweight oils for spray type application. There is; however, a twofold problem with with that approach. First, the damaging effect oil has on car parts not intended for long term oil exposure. Secondly, essential oils are extremely volatile. A deterrent spray isn't a long term solution. Unless the peppermint is contained in some sort of delayed released material, I'd imagine weekly or bi-weekly reapplication is needed to keep the furry's away with maximum effectiveness. I haven't checked or know of any studies of the actual effect mint has on rodents, but I'd guess its not actually the smell of mint(which is a complex combination of terpenes.) Rather, its the monoterpene of menthol itself that irritates their nose & eyes. Menthol oxidizes very quickly, while the smell of mint lingers on.

 

Put Mice bait in Engine compartment and areas of infestations and trash cans. Currently don't have that Issue except around old house outside

 

That's the brand headed here as in my limited rummaging it seems to be more reputable than the raft of other choices. I also have no clear understanding on the exact leaf extraction process nor resulting composition, carriers, fillers, etc.. introduced in the process. So this is certainly an empirical approach. That said the motivation for considering peppermint oil was just stocking the arsenal with whatever seemed practical in order to win the war through measured overkill. I'll defer determining the most economical and minimal repellent composition to the product minded entrepreneurs. Frankly a physical barrier where possible is my preference, then using the rodent offensive aromatics where doing so isn't possible.

The horizontal cowl area in my 2022 is different than I recall for the 2006 as closing off the rain drain exists completely appear to be more complex. I've had an '86 truck left sitting for some time where a mouse chewed a passage hole thru the plastic squirrel cage fan vanes. So a similar intrusion appears be possible through the plastic cowl cover itself particularly as the molded-in vents in the cowl cover give them a foothold. But I've yet to hear a report of that scenario.

 

$3 for a 4 oz bottle is a hell of a lot cheaper than a new engine harness.