oil heat exhaust smell/problem
I am in need of assistance. I've got a forced air oil furnace in my unused basement. Sometime last spring, I started getting an exhaust smell when the furnace would kick on. It would only last for a few seconds and would come and go- somedays we'd notice it, and somedays nothing. I had the furnace serviced at the end of the heating season and the techs told my wife that it was very dirty.
I started noticing it again this season and again, there's no way to predict it. Sometimes it smells, sometimes it doesn't. It only lasts for the first few seconds that the blower is on. While working in the basement, the furnace kicked on and I saw exhaust blast out of the damper. I checked out the damper and it appeared to be pretty flimsy. I just had a new damper installed- this one is pretty beefy and every now and then I get the exhaust smell.
I turned the thermostat up last night and ran downstairs to check the furnace. There was a puff and exhaust came out of the seams on the vent pipe. These seams are not sealed with anything.
Do I have a major furnace problem here or is the fix as simple as caulking the seams on the vent pipe? If all I have to do is caulk the seams with some high temp silicon, will I be creating too much pressure internally on the furnace?
Thanks in advance for any advice!