Heater core replacement?

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cstrand84

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kansas
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chris
Truck Year
1979
Truck Model
gms k25
Engine Size
383ci
iv got a 1979 gmc k25. bought the truck nd the guy had already took apart the heater core. i have know idea how to put it back together because iv never had one apart. so where the hell do the hoses go for the core?
 

chengny

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NH
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Jerry
Truck Year
1986
Truck Model
K3500
Engine Size
350/5.7
The heater hoses go on the heater core nipples (supply & return) where they penetrate the firewall:

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Supply is always from a nipple at the front of intake manifold:

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Return can be to the radiator - like this:

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Or sometimes to the suction side of the water pump - here:

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Camar068

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Kentucky
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David
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1986
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K10/LM7 5.3/4L60e/np208/3.73/32"
Engine Size
10 yrs Air Force
only mentioning because I haven't seen it posted. Take 5 minutes and remove the fenderwell. I can't tell you how many of these I've seen with a hole cut to get to the bolt.
 

HotRodPC

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It's a bitch but I got my bolt without removing the fender or cutting a hole with a series of extensions and wobbles. It was tough, but it's doable for sure. I've done it.
 

RustyPile

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Nick
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1983 GMC
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1500
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350 SBC
It's a bitch but I got my bolt without removing the fender or cutting a hole with a series of extensions and wobbles. It was tough, but it's doable for sure. I've done it.

Me too ---- at least a hundred times.. A 1/4" air ratchet helps immensely..
 

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