78 F-250 Heater Issue

[Goldy79]

Took a 4 hour scouting trip with my son today and the heat in my rig was virtually non-existent. The thermostat was working just fine but I could not get any heat on the windshield or floor. I've heard you can "backflush" the heater core but I'm not sure how to do that... I've also heard cardboard in front of the radiator can help too. I could really use an opinion from someone with Ford 4X4 experience. We'll be chasing blacktail bucks in November and it would be nice to have a warm rig....

The engine is a 300 straight 6, single cab, longbed.

[FC]

Can't you swap the hoses on that heater core? If so give it a whirl, it works much more often than not but worst case an old F250 heater core isn't a big deal to change.

[dewandgin]

Get the vehicle up to temp and then feel the heater hoses. One (usually the top one should be hot and the bottom one should be warm. If the one is hot and the other is cool you have a restriction in the heater core. Take the both off and flush with a garden hose from the side that was warm and see if that helps.

  Now if the hose is hot and the other is warm then you have a temp door problem on the heater  box  and that is a whole different kettle of fish.

 Check that and let me know what you find.

[diegomx3]

Is the blower coming on and it is just not blowing warm air?

[Goldy79]

The blower is working fine... just no warm air. Thanks for the tips guys... I will let you know what comes of this.

[jackmaster]

if it is anything like my old f250 76 factory high boy, it had a stock 390 in it, but the heater core went out and we had to go through the glove box if i remeber right, but it was actually pretty easy, even for a non mechanic like my dumb arse  and yes heat is always nice in november after chasing the grey ghost in the the wet and cold....

[b23]

I'm not sure if the F250 is the same as the F150 but I had a 79 F150 I had to replace the heater core in when I was in high school.  I did it by my self with basic hand tools when I was in my teens and it was pretty straight forward and easy.  The air box the heater core resides in was pretty easy to get to and dropped down from under the dash.  My 79 F150 didn't have AC which probably made the job easier as well.  The 78's and 79's are identical trucks so unless yours has AC, it's a pretty easy job to replace the heater core in one of these trucks.  I believe it cost me around $70 for a new heater core from NAPA back in 1987.

[Woodchuck]

My first word of advice is to start simple. Make sure the mechanical valve in the heater hose is moving. If the linkage is moving be sure when it moves it makes a difference in the temp of the hose, the flap can be broken and stuck in the close position.  The valve will be in a heater hose probably a foot or so from where the heater core ports poke out from the box.

[Goldy79]

FYI - Back flushed the heater core and WE HAVE HEAT! It's not heating me out of the truck but it's enough heat to make it bearable. Thanks for the help guys!

Now to reseal the rear diff... tits or tires right?

[C-Money]

Glad you have heat!!

[Griiz]

Make sure the heat control valve in the hoses is moving when you slide the switches on the dash. It could be the cable or valve is messed up and no coolant is flowing through the heater core.