Water circulation diagram 2002 Lincoln navagator blows cold air

check that the thermostat is in correctly as it will cause no circulation but overheating. have a compression test done to eliminate head gasket /cracked head. There could be a blockage in the heater core but I am thinking that by passing the heater fan he has also by passed the actuator( coolant valve) for the heater core. Water pumps suffer from bad bearings and very seldom anything else. check that he hasn't blocked off the water to the heater core as well
the throwing back of the coolant is the boiling of the coolant in the block ( bad head gasket) due to lack of circulation. It may be a blocked radiator as flushing doesn't fix the blocked cores . If that is the case a new radiator is in order.

Sounds like the blend door or blend motor is not functioning/opening. This door allows the heat/cold air to come in by adjusting open, closed or anywhere in-between for temp. Start there. They are usually vacuum controlled and mounted under the front dashboard near the knee board.

Water pumps go bad when they leak. If there is a lack of circulation, there could be a clog in the system. Is the heater core getting hot on both tubes at the firewall? If not, then the heater core is clogged up. Has anyone ever put too much sealant into the cooling system that would cause an overheat condition due to lack of circulation of coolant?

Good luck on this repair.

Heater core could be blocked up, or the blend door is stuck on the cold side of the a/c evaporator or the blend door is stuck in the cold position.

check hot water is circulating through heater rad by feeling the inlet and outlet pipes as they come thru the bulkhead if ok it sounds like there is a control panel prob, if hot water isnt circulating make sure cooling system is bled properly, and you could try backflushing the system.

it's located on the accumulater. an silver colored bottle near the firewall

First scan for codes. Is it a v8 0r v6?

1st you need to make sure no air in your system open you radaiator cap and your heater to max and see if air bubles or circulation is going on fill up accordingly otherwise you have blockage in your system or water pump if no circulation ////make sure no bubles all bubles should be gone////look for coolant circulation in your radiator make sure your thermostat is not defective or placed in the right position.

try changing the thermostat if thats not it check and see if you have water leaking in the passenger side floor board if so then you need a new heater core

If it is the blower motor that isn't working you shouldn't have cold air blowing out either, if that is not the case, and you have cold air blowing out the vents I would guess that it's a problem with the blend doors. They redirect the flow of air to change the temp.