I am an owner of a home in the NJ area and have a problem with the plenum in an oil furnace which appears to be cracked. There is a little residue on the wall near the heating vent and a slight oil smell. What would cause that to happen in a furnace from Inter-City Products that is about 12 years old? The basement air intake vents have been sealed because the basement is used for antique refinishing, sanding a painting. There is another air intake vent upstairs. Could this cause the problem?
How much should the replacement of the phlenum cost or is it just as expensive to replace to whole furnace?