We seem to be overrun with squirrels this year. They seem to be everywhere and into everything. A daily battle.
Lately, they really seem to like our vehicles, for some reason. We've lived here over 30 years and never had this problem.
Yes, the vehicles are parked outside. One car is covered, also the motor home has a cover.
They're building nests, and storing pine cones, under all of the hoods.
Now, chewing the firewall insulation to build their nests, and then chew on the wires.
They just chewed a coil wire, and moved on to the injector wire.
Big money! Anyone else dealing with this?

Probably mice not squirrels....

Mice will chew wires in outdoor vehicles but probably wouldn’t drag pine cones up in there.
Squirrels will. Maybe have two seoerate rodent problems.

Some people have had luck with dryer sheets up in the engine area. Wrap them around the bundled wires with zip ties. They don’t like the smell. Likewise putting moth balls in mesh bags and securing them up in there.

We have tons of squirrels (red, gray, chippy, ground) and the only thing we've ever had try to make a home in an outside vehicle is pack rat.

Pine cones = squirrels. Not mice.

were there any "odd" objects in the nests you found? shiny stuff?

Tape large cotton balls in and around the engine of your vehicles. Douse the cotten balls with peppermint oil. I can't stand the smell of peppermint; besides the smell making naucious. However, it keeps both mice and squirrels away from my vehicles. I started this after I watched a squirrel climb up the tire and beneath my vehicle. Ever since I started this, no more issues.

I just wish there was some other scent I could use besides peppermint. I can't stand peppermmint!!

Good luck.

No "odd" objects in the nest. Just dried grass, bits of the firewall insulation and a bunch of pine cones.
In the Jeep airbox, I found a pile of just pine cones. No nest.
We can see Mr. Squirrel running around with a mouthful of grass. Haven't seen any mice around.

most likely a MS squirrel getting ready for birth. a gray squirrel? I only see them collecting pinecones. so industrious. Do you have a box you could put next to the jeep, cut a couple of small holes and move all the stuff into it? I keep batting out back on our deck for the pine squirrels, they love it for their nests

The European cars have soy wire insulation and the wildlife like to eat it. There is a capsaicin tape that you can wrap around wire harnesses.

I did this on my wife's car and it seem to deter them.

Of course, it does not help with the firewall.

Got another odor you like? Try using it as long as it is a strong odor. The concept is that the critters ability to smell presence of predators is taken away so they will find somewhere else to go.

We've had a very busy squirrel, apparently. I opened this cabinet for the first time in awhile. A few peanuts rolled out. Then, as I opened the door all the way, an avalanche of about 25 pounds fell and had to be dug out. Even the VCR was packed full of them.

Squirrel? or perhaps a prank?