Recently I've been getting a rubber or plastic smell coming from my heater in a 1999 cavalier, it almost smells like armorall. This only started when I had to use the heat and is overwhelming inside the car but not outside. I did find a small amount of oil leaking on the manifold, but I was thinking this might be a heater core issue. Please help out.

Thanks,
Dave Thomas

 

TTT

 

if you've cleaned the engine recently that might be the cause.