Help with no heat please

[cochino12]

So I removed my 4.3 for a 350 and now I have no heat in the cab. Upper radiator hose gets hot, truck warms up to normal temperature, lower radiator hose and both hoses to heater core are cold (one to intake other to radiator).

Any ideas? Thanks

[Ski-me]

plugged hose? Did you run engine from cold with radiator cap off to try and get the air out of system? Thermostat?

[crazeetxn]

So it will get to normal temp but not overheat? And still the hoses are cold? Was hoping it would be a thermostat issue. Easier than a heat core. Stick a water hose up to the heater core hoses and see if it flows or if it's clogged.

[Ski-me]

when I changed my water pump, I drove it and started overheating. I pulled over and felt my upper radiator hose...cold.

Let the truck cool down and then pulled cap off of radiator. Ran it, topped it off and then no more issues. So my problem was just burping the system, so to speak.

[truckin 79]

yeah you might just have air on the system. Do you have a overflow reservoir hooked up to radiator?

[Prerunner1982]

If the old engine was not out for very long and the heater worked with the old engine I would be surprised if the heater core is plugged. If the engine was out and the hoses disconnected for a bit I suppose something could have got in there and clogged it up.

Try bleeding the coolant first and go from there, hopefully it's that easy.

[cochino12]

thanks for the input guys. I think the problem is a clogged heater core, tried flushing it out and a whole lot of nasty sludge is coming out.

Do I need to drain the rest of the cooling system now? Coolant looks ok

[geezer#99]

Could be heater hoses hooked up wrong.
Intake to bottom on core.
Top of core to rad.

[wilkin250r]

I have seen a rare instance when the heater core was partially plugged (I think the previous owner used a radiator stop-leak too many times), and only one or two coils in the heater core were open. As a result, you could indeed get a water flow through the heater core, but no significant transfer of heat.

When we changed the heater core, it cooked him out of the cab. I took the old core and cut it open to verify what the problem was.