heater core feed side

[87351ranger]

What feeds the heater core? fitting next to the thermostat or the water pump fitting. Not getting heat inside the truck. Motor up to temp 1908. Vents will read 120-125* at idle then when you drive will go down to 90-100*. would seem hot but isn't. Entire cooling system was replaced about 4000 miles ago. Heater hoses going to the heater will both get hot, than after you drive it the one going to the waterpump will be cool, believe this to be the return line. Rad is always filled when checked and overflow is too, no leaks detected. I know its something stupid that I am overlooking. Going to pull the heater hoses off and check to make sure heater is not plugged. Sometimes the heat works good and other times it doesn't, mostly doesn't. Should there be a restrictor in the return side?

 

[adsm08]

Should have no restrictions. The heater core doesn't care which way coolant flows through it, but yes, your colder hose is the return.

Sounds like a restricted core to me.

 

[RonD]

+1 ^^^^

The heater core is just a mini radiator, and there is no assigned in and out, engines side has an in and out but core can be hooked up either way.

In fact you should reverse the hoses at the firewall every 1 or 2 years to reverse the flow thru the core to keep it cleaner

Yes, the hose by thermostat is the OUT to heater core
Water pump is Return from heater core

Heater core can show good flow with garden hose but is still blocked at the lower end, so only top area of core is getting hot, not the whole core