One of my cars, mainly driven by my daughter, but sometimes by my wife. I myself rarely drive it. Recently they told me it had acquired a very strong smell, and indeed it had. (I mention this because for me it went from having no smell to having a very strong one - it might be that in reality it was more gradual, but they don’t remember.) We subsequently identified it as being a mothball type smell.
Question is how in the world this might have come about? Neither have put mothballs in the car, and I don’t think we even own mothballs. Is there something else with a similar smell that might have gotten in there?
[It doesn’t seem to be anything mechanical - which was my initial concern. The engine compartment has no smell, nor does the air coming from the vents. I’ve sniffed the exhaust but it smells like ordinary exhaust to me. The trunk smells about the same as the car interior.]
There are two different types of moth balls. In one type, the main ingredient is naphthalene, and in the other it is paradichlorobenzene.
It’s naphthalene that has the smell we all think of as mothballs, but it has largely been replaced by para-dichlorobenzene which is less hazardous to humans. Naphthalene is mainly derived from coal tar.
Years ago I worked briefly in the garment industry and a lot of our imported cloth was treated with naphthalene as a moth and insect repellent. Is it possible that your family have been carrying any new or treated cloth in the car?
Possibly a coolant leak via the heater? Anti-freeze/coolant might be mistaken for mothballs…although I see you say you checked the vents and detected nothing…
Is there a bottle of T-Cut very slowly leaking under a seat in a way you won’t notice (apart from the increasing but for some reason unidentifiable smell) until it’s ruined a big section of carpet? Not that I’d ever be so foolish as to leave a bottle of T-Cut in my car through a hot summer, you understand. It’s just a wild guess.
If it’s a heater leak, there’ll be a strong sweet-ish smell and your windshield will fog up and stay fogged, no matter how long you run the defroster.
Could be mice; their urine smell is just awful. Check under your seats, in the trunk, for that ball of fuzz that they build as a nest. Their droppings are little dark brown rice grains. Several times on my cars, mice have built a nest in the heater fan; if it makes a vibrate-y noise when you turn it on, well… I’ve gotten to be quite expert at pulling the fan out in jig time. All three times, I finally excluded them by pulling off the cowl panel at the base of the windshield and gluing a piece of wire screen over the ventilation system air intake.
