I used aluminizied steel gutter guard to screen the intake to keep mice out.  Because it is against the soft hood gasket, i covered the metal with tape. 

We do similar down at the service station. When we are doing oil changes we check the air filter for a mouse party. If so Dan has a roll of steel mesh screen for that purpose.

Every vehicle / air duct cleaner is different...  have to be creative at times. 

Edited August 8, 201510 yr by flagmanruss

I camped for 9/10 hours at a campground, got in the truck the next morning to start and a chipmunk was scolding me out front of my truck. I became suspicious and popped the hood and found he had chewed the soft rubber cap on the proportioning valve. That Turkey!

 

Now a couple years later a chipmunk was at my back door on the wet side of Oregon. We don't have chipmunks around here, do we?.

Hadn't opened the hood for a week or so, and look what I found! Really ticked me off!

My truck came with the insulation package...  I tried to tighten it up but it was just super mouse habitat.  I ripped everything off the hood & the upper cowl box...