When the engine has warmed up there are puffs of smoke coming out from the air vents on top of the dashboard on my 1966 E type 4.2l 2+2. It seems to come from the heater, but there are no leaks visible. Any advice warmly welcomed. .
Check to see it that is smoke or steam. If it has an anti-freeze smell or fogs up the windscreen, it may be a leaky heater core.