No heat

[hanson1287]

So I have a 97 F150 w/a 4.6. It will not blow heat at all. We replaced the thermostat already and the temp gauge is normal. After that we tried a backflush of the radiator to no avail. The only thing left on my mind is heater core but it is not showing the typical signs. I have no film on my windows, no coolant smelled in the truck along with no drips of any kind and the floorboard on the passenger side are bone dry. Any ideas?

[Archerysniper]

Try back flushing the heater core lines had the same thing happen on one of mt trucks the heatercore was plugged.

[Jeremy airjer W]

Check to make sure you hear a difference in air flow when you switch from full cold to full hot to make sure the blend door is opening.

If that checks out than back flushing the heater isn't a bad idea.

[Scott K]

Feel the heater hoses going into the heater core, are they both hot? Is one hotter then the other?

[motley man]

Change radiator cap as sometimes they go bad and don't hold pressure. I have seen many of these bad in Fords. I have 4 Fords.

[Jeremy airjer W]

Change radiator cap as sometimes they go bad and don't hold pressure. I have seen many of these bad in Fords. I have 4 Fords.

It's not leaking and its not overheating. I can't think of why a bad cap would cause no heat without one of the other symptoms?

[hanson1287]

Blend door is workin good. I am going to backflush the heater core monday after the holiday and let you guys know how it goes

[hanson1287]

So update on this after many failed attempts. We tried the backflush of the heater core and it was plugged up so new heater core installed. Still no heat. Thermostat was re-replaced so now its the second one in as many weeks. Temp gauge was fine before but now is fluctuating between hot and cold. Today we got it back from the mechanic after all that was done and it was blowing heat and then all the sudden it stopped. I checked the antifreeze level when I got home after an hour of driving. I accidentally took the cap off too fast and antifreeze sprayed everywhere. Not so much as a flinch to me from it, it was like room temp. Felt the top hose to the radiator and it was warm but not hot. The two hoses that go to the heater core were not hot at all. Anybody have anymore suggestions? This one is even stumping my actual mechanic.

[croixflats]

Water pump? If the antifreeze was warm and not hot radiator liquid may not be circulating fast enough.

These stumpers are frustating. Sometimes when fixing one thing it leads to another related part failing.

[deadeye]

Do the heater hoses go directly to the heater core from the motor or is there something in between them? Some older vehicles had a heater control valve that would block off hot water from getting too the heater core. IDK for sure if that year and model has it but its worth a look under the hood.

[fishing tech]

Just had 1 where the foam on the blend door came off and would not let the door move in full range. So you would not have full heat or full cold. And this is not the first time we have seen this.

[jeffreyd]

have you replaced the heater hoses? could you have a hose that is coming apart and collapsing? you could also try to cover the grill to see if the temp comes up, might be too much cold air across the raditor not bringing water temp up