Overheating and no heat

Good morning.

The fact that it has overheated many times tells me that there may be damage to the head gaskets. That is when compression leaks into the cooling system and injects air into the system. The heater core is at the top of the system and that is where the air will settle. A leak down test will verify if that is the issue. Very common issue for this engine.

You can try bleeding the system as well to see if you can get any heat. Remove the radiator cap and have someone inside the van and run the engineat 1200 rpm. Watch the coolant level and add as needed until you get heat inside the van. You can try this to see if you can get heat.

Does the temperature run normal now that you have changed the thermostat?

Roy