Heater Emergency!!!

[1972GMCsierra4x4]

So temps finally dropped off to winter here in Kansas and my heater still may as we'll be an air conditioner. Swapped cores, put in all new heater gaskets and nothing has helped even after I let my truck idle and warm up for 10 minutes. Any advice/help would be greatly appreciated

[cdowns]

a 190 radiator thermostat and good antifreeze

[Tom Vogel]

Have you put your hands on the heater hoses to see that they are warm and that the coolant is circulating in there? Is the heater valve opening and closing? And, of course, youve got the radiator topped off and full, right?
That thing should toast you right out of there.

[Longhorn 70]

I'd check the heater valve. BEWARE there are 2 types that look similar. One that opens on vacuum and one that closes on vacuum. I think we want the close on vacuum type.

As Tom said check the heater hoses. Make sure BOTH of them get hot.

[1972GMCsierra4x4]

How hot are we talking? Both get pretty warm after the truck runs a little

[1972GMCsierra4x4]

Hoses, that is

[Andy4639]

Check the cables on the dash unit. Make sure they operate the door for the hot air. Just because they slide back and forth doesn't mean anything. U have to watch and see them working.

[Lee H]

My heater will not blow hot air after just idling. It takes being driven a few miles and then it heats up slowly. After 3-4 miles it's really hot.

[Mr Chevorlet]

I would say also check to see if the flapper door inside the heater box is open to let the heat from the heater core to blow out.

[463]

Originally Posted by Lee H

My heater will not blow hot air after just idling. It takes being driven a few miles and then it heats up slowly. After 3-4 miles it's really hot.

You will have to have a system pressure test to see if there is a leak. in most cases you rad cap is weak. Systems need 15 - 16 lbs psi to work right when it's cold. Start by replacing the rad cap first.

[1972GMCsierra4x4]

Thanks for all of the help guys, I really appreciate it. As it turns out, my radiator wasn't completely full. I topped it off before I went to class this morning and I'm going to burp my coolant system during shop today to get all of the air out (just in case). I'm not sure if my blend door is working right, but I think it is because when I move the lever, the air flow through my floor vent changes. I'll make sure it is when I replace my in-cab gaskets either tonight or this weekend. As for y'all who said to check my heater valves, I forgot to mention that the one of the POs by-passed them and installed straight hoses.

[1972GMCsierra4x4]

One more question. How do you guys have your heater hoses routed? I've got the one from my water pump going to the inlet of my core at the bottom and the top return line going to the radiator. Is this right or wrong? The PO had them routed this way so that's how I did them.

[Lee H]

Originally Posted by 1972GMCsierra4x4

One more question. How do you guys have your heater hoses routed? I've got the one from my water pump going to the inlet of my core at the bottom and the top return line going to the radiator. Is this right or wrong? The PO had them routed this way so that's how I did them.

OK, that's why you have little heat. A better routing is intake to bottom of heater core, top of heater core to radiator or water pump.

[1972GMCsierra4x4]

Glad to say that my heater works awesome now! Thanks to all who gave advice!