I have a 2003 Pontaic Montana, it is over heating and the heater is shooting out nothing but cold air. What can I do?

First a little lesson on your cooling system. You will have your radiator which will have coolant running through it and the fans will remove the heat from that radiator by pulling air across the fins, the wind does this while driving, thus keeping it "cool". The only way your coolant flows is when your thermostat opens at the temperature required and the water pump pushes the coolant through the hoses, radiator and engine to keep everything at operating temperature. The coolant that leaves your engine is hot, it has picked up the heat from your engine and is heading back to the radiator to be cooled off. Before making it through the radiator it passes through your heater core which heats your vehicle the fan in your van will blow through the heater core (looks like a mini radiator) and the hot air that blows through it heats your vehicle through the vents.

Now, if you have no heat and your van is overheating then it is safe to say that your coolant is not flowing or its blocked. You will need to start the van and check your hoses. If the hoses are worn and collapse or pinch together then you will need a new hose, after that if its still not working replace the thermostat first to ensure that its not locked up, and if the problem persists I would go for the water pump. Those are the only two things that will stop flow. The radiator can get stopped up, but usually never FULLY stops flow. You will have minimal heat, but for no heat you definitely have no coolant reaching your heater core.

Let me know what you find or if you need further assistance.

Start by replacing thermostat. common symptom