Inadequate Heat

LateOnTheBrakes · Dec 17, 2021

The heat in my K30 has been inadequate at best since I got the truck. I tore into the HVAC box today hoping to find a blend door malfunctioning, a rodent nest, or dirty heater core but everything looks fine. Is there a design flaw with these systems or what should be my next step?

LateOnTheBrakes · Dec 17, 2021

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Dave M · Dec 17, 2021

1, have you back flushed the core
2, how/where are the heater hoses connected to

LateOnTheBrakes · Dec 17, 2021

I'm not sure what you mean by backflushed. I filled the heater core from the top fitting with the lower hose connected. Fluid float easily through both fittings and I can blow through it without any obstruction. My hoses run parallel to the inner fender back up to the heater core. But I have a 5.3 Silverado motor swap so the way I explain the water output on the water pump may not make sense for SBC and BBC folks.

LateOnTheBrakes · Dec 17, 2021

I guess a follow-up question I have is which is the inlet and which is the outlet? The way my brain works I would think you would feel from the top and let gravity return it through the bottom. But I ended up just matching the big tube on the heater core to the big tube on the water pump and small to small.

Dave M · Dec 17, 2021

Backflused is basically what you have done, and Yes, I'm now at a loss with the 5.3L

Dave M · Dec 17, 2021

The larger tube on mine connects to the radiator, so the smaller is the inlet.

LateOnTheBrakes · Dec 17, 2021

The LS has dedicated outputs for heater core.

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AuroraGirl · Dec 17, 2021

LateOnTheBrakes said:
The LS has dedicated outputs for heater core.

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is the stock truck its from use a flow restrictor or something to reduce the GPM of the heater core? You could be moving it way too fast for it to actually transfer good heat, that looks like its unrestricted and its just a loop that the water pumps full capacity probbaly circulates. also I would change the clamps on your nice hoses before they dig in over time

AuroraGirl · Dec 17, 2021

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quite interesting I found this to suggest going to the surge tank before going to the engine after the heater core

your heater core is also an old brass one, it could be that new aluminum ones can transfer it faster/better like all LS vehicles were made with
hows thermostat? what kind? using green or dex?

Dave M · Dec 17, 2021

I assume you are running an engine thermostat ?

LateOnTheBrakes · Dec 17, 2021

Yeah. 195*F thermostat. I ever set the electric fans to not come on until 210*F to see if that helped. Not much.

LateOnTheBrakes · Dec 17, 2021

AuroraGirl said:
quite interesting I found this to suggest going to the surge tank before going to the engine after the heater core

your heater core is also an old brass one, it could be that new aluminum ones can transfer it faster/better like all LS vehicles were made with
hows thermostat? what kind? using green or dex?

It's not brass. It's aluminum and looks really good. Thermostat is less than a year old and I know it's opening, but the heater core output on the LS is before the thermostat. Dexcool.

bucket · Dec 17, 2021

Did the poor heat condition exist before the engine swap?

Memaloose · Dec 17, 2021

I was going to suggest the thermostat. Check your engine temp gauge or if you have an idiot light, use a thermometer to check the engine temp. If your thermostat is stuck open, you wont get much heat.
Also, make sure there's no air in the system.
It's usually one if not both of those problems.

Inadequate Heat

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