How Hot is Too Hot?

Just looked at an old Heil gas furnace. Fan sounded labored and vent pipe near the furnace registered 197 degrees. Never felt so much heat going where it wasn’t supposed to. Is this a sign of trouble?

Define ‘old’. Also, I know it’s obvious, but did you actually remove the filter and inspect it? You’d be surprised how often the obvious gets overlooked. (Perhaps the cat went missing and is stuck in the return trunk)?

How hot is too hot? If it’s over 80°, I’m turning the cooling system on!

No, it’s a sign the system is functioning normally.

The vent pipe will get very hot.

Did you check for clearances to combustibles? Is it single wall, or B vent?