96 f150 4x4 351 auto.
Still cant get any heat.
Just replaced heater core upper,lower radiator hose,bypass hose,water pump,both hoses to the heater core. Flushed system 3 times. Tried switching heater hoses around thinking i got them switched around.
3 new thermostats.
Im lost. when the truck is running all hoses are hot too the touch.
No vacuum leaks that I can find.
Only thing that is a little bit strange is that when you accelerate you can hear the coolant go through the heater core.
And I have burped the system so there is no air locking.
Im fixing to junk this truck out! Ive tried everything I can think of. This is a new one on me.
Any suggestions? Hate to take her to the scrap yard shes a nice truck but I cant drive this thing with no heat.

 

Are you sure the blend door is working properly? Check vacuum lines to heater box a friend of mine had his disconnected..I reconnected it and he now had heat

 

checked that already but I will recheck. actually going to recheck all I can think of again and will give u a update
Thanks

 

If you can hear the coolant circulating through the heater core that means you have air in the system. Normally you shouldn't be able to hear any fluid in a properly bled system.

Another tool that's might be handy in diagnosing the problem would be an infrared heat thermometer; the kind where you point it at what you want to measure and squeeze a trigger. They are quite inexpensive now and come in handy for a lot of diagnostic uses. Using one would allow you to get accurate measurements of temperature in the loop to determine where the flow is or isn't going. It would also allow you to see the temperature of the surface of the heater core.

If all else fails, move south.

 

ok truck running heater core and water all good got cover off the heater core box. heater core putting out lots of heat.
Problem is with the blend door
blend door opens and shuts good but does not seal off all of the cold air?
there is a ton of cold air coming around from the closed blend door it feels like the foam sealing tape from the factory is intact . So where is all the cold air coming from?

 

The heater core surface is really hot but there is so much cold air coming thru the haeter box when the blend door is shut it just makes the heat barely warm.
Im about to get my duct tape out and tape that door upand all the places i feel cold air

 

Is your blend door vacuum operated? (Sorry don't know the internals.) If so, is it possibly not shutting all the way due to vacuum leak or bound up hinge? Also, even though the gasket is still there, is it soft and pliable? As a temporary experiment you could duct tape the door closed to see if you finally get good heat. Sounds like you're on the right track though, too much outside air coming in.

 

sounds right

 

Make sure no cold air is bypassing around the heater core itself where it fits into the box. It should have foam around it the seal it up.