Furnace port, and combustion chamber crack question.
These are pics of pretty old Lennox oil furnace. The model on the furnace and blower is OH4-80S-Z, serial no : G 121294. I don't quite know the age but the furnace works well, serviced every year by a tech. The service card hanging from the unit shows 15 years of service data, all indicating that the units combustion/co were good.
In an effort to get some of the soot out, I opened up the unit and found two things
1) there seemed to be a port at the bottom covered with furnace cement and filled with loose insulation. What could this port be for? Also is it normal for it to be covered with cement?
2) Also, there is what looks like a hair line crack in the combustion chamber. Is there anything I can do to prevent it from getting worse.
Attached some pics. Appreciate some help from all you helpful pros out there.
If there is any other info needed, please let me know.