could be head gasket problem. does your heater work? might need heater core , clogged up. do compression test. or bypass heater core and see if that works.
this is not an answer just an update. coolant is filled
Remove the water supply hoses from your 2002 Dodge Ram 1500 heater core. Remove the heater core retaining bolts. Reverse the process to install the new heater core.
The easiest way to check is to feel the heater hoses going into the firewall. Check the hoses from a cold start and check that both hoses get uncomfortably hot at about the same rate. This is a good indication that coolant is flowing.
Remove the water from your 2002 Chevrolet Camaro cooling system. Remove the water supply hoses from the heater core. Remove the heater core retaining bolts. Reverse the process to install the new heater core.
Purg The Air Out of the Cooling system
possibly clogged heater core, remove heater core hoses and flush with a hose until clean. reinstall hoses fill with coolant and let it run. if heater core is too plugged up you will have to replace it.
At the back of the engine on the coolant outlet that goes to the heater hoses on the firewall.
the inlet heater hose that connects to the top of the water pump connects to which outlet on the heater core? the far outboard or the inside? this is in a 2002 ford f250, 7.3.
The heater core is located in the center of the dash inside the heater unit. If you look under the dash on the passengers side you will see, from right to left, a blower, the AC box then the heater unit where the core is. Also, in the engine compartment you will find two coolant hoses that enter the firewall near the center, those hoses connect directly to the heater core.
Could be the blend door, could be the air intake for the HVAC system, could be a clogged heater core. If the AC works without issue, I'd suspect the latter. You simply detach the heater hoses and flush them.. I prefer to use compressed air and some CLR when I do it, but you can do it with water.
Remove the hoses going to the heater core. Use a regular water hose with a high pressure nozzle and flush both ways.
Give us the symptoms you are experiencing with your 2002 S-10? or Silverado? Such as, leaking coolant on passenger floor. lack of heat. sweet smell when heater is blowing.