Heater core

[rwljpl]

My truck has never had working heat (it does have working a/c)
The previous owner said the heater core was probably the issue
I just got around to changing the heater core
But I still don’t have heat
The air blows somewhat warm but never really gets hot
If I let the engine get up to running temp, the heater hoses do not get hot at all (the bigger, upper hose is cool and the lower, smaller hose is barely warm)
My antifreeze level looks ok
The fact that the air gets slightly warm makes me think it’s not a blend door issue - and it looks like the blend door works when I slide the a/c controller
What else could be wrong? What’s the next step in troubleshooting?
TIA

 

[Blue Ox]

From what you're describing I'd go back to 'the hoses don't get hot.' So I'd guess either a plugged fitting, or it's plumbed wrong. Pics of the hose routing and connections would help here.

 

[Shorty81]

From what you're describing I'd go back to 'the hoses don't get hot.' So I'd guess either a plugged fitting, or it's plumbed wrong. Pics of the hose routing and connections would help here.

I'm with Ox, your hoses are plumbed wrong. I have have been down that road before. You don't have flow

 

[PrairieDrifter]

Yep, has coolant in the core but no flow, explaining the warm air and slightly warm hoses.

The big hose should go(marked in blue) either to a nipple on the radiator, or to a hose barb at the top of the water pump.

The smaller hose should go to a hose barb fitting, that is straight over to the passenger side of the intake, from the thermostat housing. (Marked in green)

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[Dave M]

Could be a blocked core on the water side. Disconnect both hoses from the engine and radiator. Hook up the garden hose to the larger hose and back flush it to waste. Swap over a couple of times until water comes out clear.
If the blend door was shut l would expect hot water to be going through the core and not losing any temp when it it comes out the outlet.

 

[BigDaddy72]

Does it have a thermostat in it and does it work? What temp tstat is it? How cold is it where you live how big is your radiator ? Is your radiator full to the top?

Check the simple things first...

 

[rwljpl]

I checked the hoses this morning - larger top hose runs to radiator
The smaller hose goes to the water pump (pictured)
Are these the correct locations - the hose sizes fit, so I figured it had to be

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[rwljpl]

The thermostat works
The engine temp does fluctuate a good bit, assuming the gauge is accurate
Sometimes it’ll briefly go above 210 but then come back to probably 190, maybe slightly lower

 

[Dave M]

I checked the hoses this morning - larger top hose runs to radiator
The smaller hose goes to the water pump (pictured)
Are these the correct locations - the hose sizes fit, so I figured it had to be

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l would think that to maximize your heater temp, you need to move the hose from the water pump to the plug location on the intake manifold to the left of the t'stat housing.

 

[Powerhouse Ranch]

l would think that to maximize your heater temp, you need to move the hose from the water pump to the plug location on the intake manifold to the left of the t'stat housing.

it's not doing anything important on the water pump? you can easily just swap that?

 

[Dave M]

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it's not doing anything important on the water pump? you can easily just swap that?

l'm thinking it is moving water basically from the outlet side of the radiator, thru the core and back into the rad' . If they are the same size threads, it's an easy swap.
Interested in any other thoughts here.

 

[PrairieDrifter]

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l'm thinking it is moving water basically from the outlet side of the radiator, thru the core and back into the rad' . If they are the same size threads, it's an easy swap.
Interested in any other thoughts here.

In my experience the smaller 5/8 hose always goes to that fitting next to the thermostat, regardless of where the other hose goes. Other than that the only two places I've ever seen the other hose go to is the fitting on the radiator or the top of the water pump.

Has the truck ever had a water pump?

 

[PrairieDrifter]

79 k10, small hose to intake fitting, big hose to water pump, been this way at least 30 years. Still cooks you out of the cab in -30

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[PrairieDrifter]

Also some rads don't come with the fitting on them, just inlet and outlet and trans cooler fittings if it is an auto truck.

 

[Bextreme04]

it's not doing anything important on the water pump? you can easily just swap that?

No it's not doing anything there. On the BBC it would be a fitting with a hose to the intake. In this application I've always just seen it plugged and the plug shown at the top left corner of his pic should be swapped with that fitting.