Only luke warm heat.. even after I replaced stuff

[hey its me]

First Chevy here.. First truck I might add too. The heat has never worked in my 81' sbc c10. I at least need defrost. I live in Seattle. I replaced the water pump, thermostat, coolant, flushed heater core yesterday, still no heat. The blower motor only blows cool air. The in/out heater core hoses are like warm to the touch even after the truck is warmed up. Ideas?

Thanks-Ian

[weider1717]

Originally Posted by hey its me

First Chevy here.. First truck I might add too. The heat has never worked in my 81' sbc c10. I at least need defrost. I live in Seattle. I replaced the water pump, thermostat, coolant, flushed heater core yesterday, still no heat. The blower motor only blows cool air. The in/out heater core hoses are like warm to the touch even after the truck is warmed up. Ideas?

Thanks-Ian

It's your core try doing a reverse flush on it.

[75C10]

You have to move the heater hose from the water pump into the intake manifold. There is no pressure on the water pump the way you have it hooked up. The pressure is upstream of the thermostat. Move the temp sender thats in the intake and connect the heater hose at the same point. Put the temp sender into the cylinder head. Then it will all work fine.

[hey its me]

Thanks guys. Ill find a 90 degree barbed elbow, move that hose, and plug the hole at the water pump. I'll reverse flow that SUMBICTH heater core too.

[75C10]

If you have already flushed the heater core, doing it again would just waste anti freeze. Change the hoses and it will probably work fine.
Darwin

[rich weyand]

One more thing. There is usually a huge (~1") gap between the defroster Y tube and the heater box just above the hump. Use some metal tape (not "duck tape", but the actual tape HVAC guys use on ductwork) to seal that on three sides. The front side will be up against the firewall, so you can't get tape in there, but since it is up against the firewall, it's sort of sealed there anyway. Just look underneath the dash and you'll see what I mean about the gap.

Once you seal that, you will get the full flow of the blower up the defroster.

[barry1982]

I had a 76 a few years ago that wouldn't throw any heat. Tried everything....
Finally ripped out the heater box and discovered a Bic lighter had somehow fallen inside one of the defroster vents and dropped into the heater box.. The lighter prevented the door in the heater box from sealing outside air. So basically the heater was throwing heat, but was mixing with cold air as well.
The truck had great heat after that.

[87 STEPPER]

Originally Posted by barry1982

I had a 76 a few years ago that wouldn't throw any heat. Tried everything....
Finally ripped out the heater box and discovered a Bic lighter had somehow fallen inside one of the defroster vents and dropped into the heater box.. The lighter prevented the door in the heater box from sealing outside air. So basically the heater was throwing heat, but was mixing with cold air as well.
The truck had great heat after that.

There's one more reason why smoking is bad for you and your truck! Lol

[TrailerTrash]

kinda funny about the lighter lol

when i got my k10 two years ago it wouldnt change defroster/heater/vent/ect. so i discovered the line from the vacuum canister to the cab had come off. i hooked it back up and as soon as i started the truck the flap moved and a few bucks in change and some big gawdy costume jewlery necklace came tumbling out of the floor vent

[rich weyand]

Another problem is that low-compression SBCs generally run cold. I couldn't get decent heat out of mine until I replaced the runs-all-the-time mechanical fan with a thermostatically controlled electric fan, and, in the winter, put a cover over the center of the grill. Now I can get it up to operating temperature (needle straight up on the temp gauge, using a stock-resistance-curve temp sender) even when it is 10 below.

I just used a fender protector for my grill cover, with some squares of double-sticky tape on the radiator crossmember and a couple cable ties through the grill.

[barry1982]

Up in the north country (northern Alberta) We cover our grills all winter. Some use "winter fronts" that snap on, and others use stiff cardboard slid right infront of the rad. Helps a lot with getting up to temp, and staying there.

[ChevyC102007]

Originally Posted by rich weyand

Im thinking of getting that same bumper for my 1980 you have there.
But not to get sidetracked and highjack the thread...........after a few minutes the heater in my 1980 will run you out.....have to roll down the windows in the winter,

[rich weyand]

Originally Posted by ChevyC102007

Im thinking of getting that same bumper for my 1980 you have there.
But not to get sidetracked and highjack the thread...........after a few minutes the heater in my 1980 will run you out.....have to roll down the windows in the winter,

I like the bumper. It's dead-on identical to the original -- looks like it came out of the same tooling -- except for the punch-outs for the fog lamps. I did use a better switch and switch mounting panel than what came with it, but the relay and the wiring was OK IIRC. I need fog lamps around here to see the deer on the side of the road *before* they jump out into the headlights.

[hey its me]

fixed. Heat works good. Moved the hose from the water pump to the intake manifold. Thank you all.

[75C10]

Glad to hear it works well. Darwin