Quote Originally Posted by Great-Kazoo View Post
Replace. For the time & labor involved. I'd go with a new unit. UNLESS that unit is under warranty.
I second. If its producing CO then you will have to replace. You typically need a bore scope camera of some type in order to see any cracks, as the heat exchanger is not easily accessible. Thats why when guys say there is a crack without digging into the unit or seeing CO production on a meter, they are trying to sell you a furnace under false pretenses.

Stenz- I am curious. How old is your unit?