Paint thinner smell when heat on/warm days

[gjm551]

Does anyone have the problem of a strong smell of paint thinner when they turn on their heat or drive on warm days? I have had my truck for almost a year and have noticed the smell on occasion and am wondering if it's as simple as someone spilled paint thinner or if something else is to blame, and how to get rid of the small. Truck info: early 99 f-250 td, 7.3L, 4x4.