Heat not working

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Schurkey

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Ok so I went back to the basics and I checked the hoses after a 30 minute trip they weren’t reversed. However The outlet hose was a great hand warmer in the cold but the inlet hose was hot enough to send u to the hopsital. so the coolant going out is a lot cooler than the stuff going in. Does this mean my heater core is bad???
Heater core restricted. Damaged, or plugged.

The blower is trying to cool the heater core by using outside air (inside air if recirc)
The engine is trying to heat the heater core by pushing hot coolant through it.

In your case, the water is so restricted that the air is easily able to cool the core, which transfers insufficient heat to the air--and you have a weak heater.

I just don’t understand why it isn’t getting heat. The core inside the box gets hot and the box is hot why isn’t it transferring to the vents like it should
If the outlet temp is that much lower than the inlet, the core and box aren't getting hot enough.
I don't know if it was related to the LSx swap in my truck but I had to put a restricter in the line out on the heater core to get the heat to work for me.
Bad move. The restriction belongs on the INLET side of the core. In fact, it's built-into the GM quick-connect fitting on the back of the TBI engine intake manifold. I don't know where or if it's a part of the LS heater system.

GM had problems with exploding heater cores when the engine RPM was high. The system (radiator cap) pressure is added to by the dynamic (water pump pressure) and the two together was more than the heater core could take.

Checked mine this morning...

Outside temp 34
Floor and panel vent made no difference, it was around 130 at idle.
Driving 40-mph it went up to 145. It probably would have gone a little higher but I have a short commute.

Putting it on recirc added about 5–10 degrees.

This was with the a/c on and blower on high. Turning off the a/c made no difference. Heater core is original (1998).
Yeah, I'd like to see higher duct temps than that.
 

Knuckle Dragger

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Heater core restricted.
Bad move. The restriction belongs on the INLET side of the core. In fact, it's built-into the GM quick-connect fitting on the back of the TBI engine intake manifold. I don't know where or if it's a part of the LS heater system.

20K with lots of 3,500+RPM freeway driving with no issues. ;)
 

Schurkey

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20K with lots of 3,500+RPM freeway driving with no issues. ;)
Is there ALSO a restriction on the inlet side? As said, it's built-into the quick-connect fitting.
The quick-connect fitting is necked-down internally to about 1/4" diameter, and even that has a divider through it. (Lower left in this photo)
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Core damage was more of a 5K--6K rpm thing.

I'd love to see photos of how the heater hoses are routed.
 
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scott_williams2

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Ok I changed heater core no difference. However I did notice two things one there is heat seeping thru a crack in the bottom of my box and two the tab holder that holds the core was broke and gone so the core just sits on the bottom of the box idk if this matters or not but if not I’m just gonna finish the winter with the compressor unplugged. I get decent enough heat and our mississippi winters aren’t that hot anyway
 

454cid

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...the tab holder that holds the core was broke and gone so the core just sits on the bottom of the box idk if this matters...

It's a piece of metal that screws into the plastic with one screw.... is the metal gone, or is the hole in the plastic broken? Not having that piece is going to make the heater less effective, since the air doesn't have to go through the core, just over it.
 

scott_williams2

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It's a piece of metal that screws into the plastic with one screw.... is the metal gone, or is the hole in the plastic broken? Not having that piece is going to make the heater less effective, since the air doesn't have to go through the core, just over it.
Ok yea that makes sense that may be the problem then Bc the hole in the plastic is gone. I’ll put a new clamp on and see the difference
 

scott_williams2

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It’s fixed. I got some copper pipe straps from work and screwed them in the core is now hold up firm against the seal. Blows good hot air now. Thanks for all the help y’all
 
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