Over heating

Could be a clogged heater core being you have no heat,or if you are loseing coolant you may have a blowed head gasket or head issue.

Yes....what color is your exhaust? If it is whitish....then you have a blown head gasket. When mine blew....having no heat in the wintertime was the first sign

Even a simple radiator cap......per chance.......by being unable to keep it within the specified pressure may cause a car to overheat

There are two cooling system bleeder screws on the Venture vans. IF you do not loosen the screws when refilling the cooling system you will trap air in it, causing the vehicle to overheat. One is on the thermostat housing and the other is near the water pump. they are both brass. Loosen the screws when the vehicle is cold fill the cooling system until a steady stream of coolant comes out of the bleeder. No air bubbles. Run the vehicle and periodically open the screws a bit to make sure all the air is out.

Is the dorman hose supposed to come off on a 2000 3400 Ventura van