No heat from heater

I have a 87 4Runner with a 22re the heater only blows out cold air. I replaced radiator, thermostat, heater core and heater control valve and still no heat. I’ve burped it by letting it warm up and work the bubbles out and tried a pressure bleeder I’m running out of ideas. All the vents are cleaned out and all flaps work, I checked when doing the heater core does anyone have any ideas?

 

could be a blend door. is shut on the heater core

 

Would that be the flap that allows the blower motor to either go through core or bypass it?

 

yep

 

Alternatively, it's possible the heater core is clogged. Either inside of it or outside. In other words, it's possible that there is a chunk of corrosion that broke loose from the engine or the radiator, made it through the system into the heater core, and stopped the water flow through it. Another possibility is that dust, dirt, leaves or whatever, has coated the core fins, stopping the transfer of heat from the vore to the air flowing over it.

To see if it's got a clog inside, feel the return hose. It should be slightly, maybe a little more than slightly, cooler than the intake hose to the core. If it's cold, though, maybe the water isn't getting through the core.

I had this problem with my 87 4Runner. I lived in Yuma, Az, the miserable land of dust, and my heater core, when I dug down to it, was covered in dust. So much, that air couldn't even flow through it. Also, there were a ton of mesquite leaves all over it. They're small, oval, leaves, like the size of a pencil eraser's top, and they had infiltrated to the AC and heater cores. Once I got some air in there and blew out all the dust, dirt, and little leaves, it started working great!

Have you also verified that the water can flow freely though the heater control valve, on the firewall, engine side? Easy to check. Let the engine warm up, and feel the hoses on both sides of the valve. They should be equal as far as the temperature of the water flowing through them. Assuming the valve is wide open, of course.

Good luck to you!
Pat☺

 

I tend to agree with Patrick...I'm not sure if a Preston flush kit would help or not but I would try it...if it's clogged and it could be removing hoses and heater core feed close to the fire wall...it's the metal pipe...could be clogged. Is your 4 Runner over heating at all like maybe the water jacket is clogged or trickling water through...flush the entire system...it's cheap and only takes an hour or two.