Speaking of rust, if you live where it rains, once a year you should check out the heater intake channel. It is accessible through the top of the cowl and through the kick panel vents, if you have them. Junk from trees tends to find its way through the cowl vent and accumulates in the kick panels, fostering rust. Vacuum or blow it out once a year or so to prevent the dreaded cancer. A stainless steel window screen under the cowl vent cover can help cut down on this.