Advice please. Heat problems.

[Michael_]

Still having heat issues. Things ive noticed:
Still cold outlet hose on heater core after backflush.
Only have heat at high rpms.
No puddles under truck or in pass. floorboard.
The vacuum valve does open and close appropriately. If its opening all the way, I dont know yet.
Any suggestions what else i should check. The temperature gauge stays in normal but i have noticed it gets to normal quickly. That still wouldnt explain the cold outlet on heater core. The inlet is hot to the touch. I back flushed the heater core until clear water came out. I had the water at very low pressure doing this. Maybe it wasnt enough pressure to unclog it.
Im lost on this and winter is a coming.

 

[974X4BLACKSPORT]

If the outlet hose from the heater core is cold, and the inlet hose is hot, you either have NO water flowing through the core, or the core is removing ALL the heat from the water! It is up to you to figure it out, but my "guess" is the water is not flowing.

 

[Michael_]

If the outlet hose from the heater core is cold, and the inlet hose is hot, you either have NO water flowing through the core, or the core is removing ALL the heat from the water! It is up to you to figure it out, but my "guess" is the water is not flowing.

Im lost. No water flowing through the core? Woudnt that have been resolved with the backflush if there were any restrictions? If I get on the gas in park, it'll heat right up. Should i try a little more water pressure on the backflush? As stated earlier, I barely turned the water on for it, but it did flow out without any trash noticable.

 

[Retroboy1989]

My first though is air in the system, but...

If the water pump vanes have corroded away, the pump won't be effective enough to force coolant through the heater lines at low RPM.