2001 plymouth neon heater won't blow hot air. only cold. we have changed thermostat, radiator cap and flushed radiator. not odor through vents or leaks on floor board(heater core)

It has air in the line. let ir idle with the radiator cap off for a little while and the air will work its way out. You may have bigger issues, but I do not think you need to clean heater core because you get heat sometimes. Do you see a lot of bubbles when you take the radiator cap off when running, head gasket if so.. You can take the cap loose while the engine is running, but not after you stop it, it will be to hot. Good luck

If you flushed the coolant with the thermostat in, chances are you didn't flush the coolant. Regardless, it's easiest to check the controls inside first. Does the blower fan work? Does the air flow change from floor to vent, to dash as it's supposed to? Does the A/C change temps when knob is turned from cold to hot? Post results.

fix coolant leak where hose or tube goes from overflow jug to the radiator cap and replace radiator or overflow jug pressure cap see what happens.if problem still exist your blend air door stuck or air door vacuum or electrical actuator not working not receiving vacuum could have broken vacuum hose or faulty mode switch, could be many things.could have plugged heater core check both heater core coolant hoses both hoses should be hot.if heater core inlet hose hot and out let hose cold heater core could be clogged need flushing out.

Bad heater core.

Thermostat.? if you haven't? Do it first then try it. While the car is running for a while touch the heater hoses that lead to the firewall. if one is cold and one is hot? You have a blocked Heater core. Follow the hoses back to the engine. Unconnect them both. By using a garden hose flush out the heater core do one side and then reverse by doing the other hose Lots of junk will come out so be care ful. Mistake people make is "Flushing the system" That doesn't mean your flushing the heater core.
Seeing that you have done everything else it could be the thermostat which you didn't list or the heater core being clogged. When you finished installing the thermostat and flushing the heater core out. Replenish the coolant system . If you have a bleeder on the thermostat housing? use it . loosen it and top off the fluid until you see fluid comeout of the bleeder. The system being air bound would cause no heat..

Have you checked for air in the system ? Some of the V-6 engines have an air bleeder on top of the intake manifold to release trapped air. What you do is fill the rad to the top , start the cold engine and open the bleeder untill fluid comes out meaning the air has been vented. With air in the system the heater does not transfer heat efficently. You can also vent an engine by squeezing the upper radiator hose with the engine off and cold. Never open a hot system. The squeeze method is easy. With cold engine remove the cap and fill the radiator almost to where it will spill over. Then slowly squeeze the upper radiator hose and you will see the air escape. When you release the prussure you will see the level drop slightly. Now if you do not have air in that system you will need to check the heater core flow. With everything closed up and full start the engine and let it warm up. Now feel the two hoses in and out of the heater core where it goes thru the firewall in one is cold and one is warm then your heater core is plugged. You can try a flush at this point but it usually needs to be replaced. Thanks for asking at Fixya.com.

could be a cracked block engine.what i would do is put a tarp or old sheet down park vehicle on it and wait then when you check you can look on old sheet to see where its leaking and it will give you an idea where to look for the leek if it was head gasket youd have sludgey looking whitesh foam in the oil

Take rad cap off when cool & run it for a while with the heater on (not defrost) and top up coolant as needed in rad, about an inch or 2 from top of rad. Let it run until you see rad fan come on & off about 2 or 3 times at operating temperature. Then replace cap, top up return bottle to proper level, and try that. Probably still air in system. If that doesn't cure it, I'd look at faulty or incorrectly installed thermostat, which would be a trip to shop that installed it, if it were me.

there,s a chance that your hot-cold air trap is not working

The system just needs to get all the air pockets out if you switched everything like you said look around where the radiator hose meets where you put the thermostat in, there should be something on the lines of a little nipple with a 8 mm bolt on it i will have to pull up the exact setup of your Taurus but its the same general concept your car is fine you just have a big air pocket , what else you can do is while its cold right now and the car isnt running is to go take the radiator cap off the radiator and see if the antifreeze is low now that the car has cold down since you last ran it. If so feel it up top it off in the radiator and it might hurp it self and remove the air pocket all on its own... If you need any more help feel free im always on here id be glad to help more in detail once you try that and look under the hood for the bleeder ( the thing with the nipple on it) Also if you could please rate me i would greatly appreciate it.

Thanks,
Steve