There are 3 things that come to mind: 1) No thermostat fitted - car may never get up to temp and will run cool as well as the heating system 2) Blocked heater core - Not common, unless plain water has been used or someone has used liquid head gasket fix that can plug that and the engine radiator as ...

Vent it to atmosphere and put a vacuum cap on the air intake hose. It won't cause a lean condition.

When I was standing there talking to seller about the gray Volvo, he said the firewall connection to the heater core hoses had broken plastic. A few days ago I looked and discovered it was the piping from firewall to heater core. I thought for sure I was screwed. Yesterday, I went looking for the pa...