2000 F250 heater problem..

New to me this past feb. F250 heat isnt very hot. Meaning I freeze my but off. If no blowing can feel little warmth but turn blower on full bore and cold. I replaced the blend door actuator. And now thinking on the heater core. Although when I touched the lines in and out of core they are both warm but not hot. How hot are those lines usually. Should I be able to grab and hold on to them after a 45 minute drive.. thanks

Thermostat? Do you have a winter front? Them diesel engines won't get warm like a gas so when it's cold you gotta block off the radiator to get them up to operating temp.

Back to the t-stat, does the temp gauge come up quick and level off or does it take for ever to come up and only half a$$ed at best? That's where i'd start if it were mine. Put a new stat in it and block off the grill (leave a small opening for some air flow).

Casey in SD

The lines must be hot enough that you cannot hold them. It sounds like you need a thermostat.

I have seen many reasons why there is no heat in a cab. You have suggested a main theme..heater core...Drain some of your system and save the coolant,then disconnect both hoses,rig up a connector and hook a garden hose up..flush the core,then switch hoses and flush it the other way,then hook it up.
The winter front may be a problem and your thermostat might be the problem,but I'll guarantee one of those three senarios...and theres one more...air in the heater core,I've encountered that as well.Some vehicles have a bleeder in the hose from the water pump and its simple to open and wait until coolant is coming out. You can buy a little valve and install it with two hose clamps into your heater hose and have a bleeder. If I had to bet five bucks on what it is I would say Thermostat....but its easier to check for air in the heater core than pulling out a thermostat when you are not sure. The absence of a winter front shouldn't be a real big factor here if the thermostat is doing its job..it shouldn't open until 180*,you can put a 190* in..sound like an afternoon in the shop checking out these ideas(mine and other posters) The shop I worked in had these issues come in all the time..plugged core needs flushing,air in system,thermostat gone wild...Good luck and let us know how you make out!

what year and engine ? If a gasser likely a t-stat, unlikely air trapped, could be plugged core if coolant looks really cruddy, but not a common problem. If its a diesel, the 6.4L was the one I remember having heat issues, dual thermostats that everything had to be just right and some porosity issues that let coolant bypass the stats.

Make sure that the heater core is not plugged. Is the upper radiator hose getting hot, but the heater hoses are not? Consider back-flushing it. One warning though: It could cause the heater core to leak even if you are careful and not back-flush it too hard.

Before you do anything to the heater core, make sure the truck is reaching operating temperature.

When all the stars in the universe are in align They are passing 200 degree coolant so yes you should be able to grab'em but you are not gonna hang on to them long.... Think of a very hot cup of coffee...

Settle that issue first.... The #1 cause low coolant...
I had a ranger that I worked on all day a few weeks ago... I had blown out, flushed and removed the water pump... While I had the pump off I removed both heater hoses and blew air thru them the return puked a mess of rust :shock: I went outside and flushed it with water and while I was walking back in the shop talking to myself pulled the nylon cover off to see the hose had a kink in it from improper instillation... It cost that guy a healthy chunk of change....