A gas furnace can produce CO, carbon monoxide
bad thermostat, bad waterpump, plugged radiator, or the cooling system is filthy and needs flushed out.
The drain can often get blocked so that water cannot escape leading to water ingress via the heating/cooling system inside the vehicle.
Low coolant? Cooling fan not working? Bad thermostat? Cooling system airbound? Water pump not circulating coolant? Radiator core plugged or restricted? Bad radiator cap?
Heating zinc and sulfur together can produce toxic zinc sulfide fumes, which can be harmful to the respiratory system if inhaled. Additionally, the reaction can be violent and may result in splattering of hot molten zinc.
Sounds like a bad switch or solenoid.
You may have a bad or weak cooling fan sensor.
a bad seal?
Blown fuse? Bad blower motor? Bad resistor pack at blower motor? Bad switch?
It is self bleeding, if you are having trouble with air in the cooling system, it may be as simple as replacing the radiator cap or as bad as a bad head gasket and or a cracked head.
it has a bad head gaskit
No completely separate from engine/cooling system
Low coolant? Stuck Thermostat Cooling fan not working Water pump not working Clogged radiator System airlocked Defective radiator cap