heater hose placement - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**tjc** · 05-31-2022, 08:44 AM

I have seen it done in both directions, 68 c10 with 350 non air truck. Heater core 3/4 fitting at top and 5/8 on bottom. from the water pump to the heater core, top or bottom?

BASE · 05-31-2022, 08:53 AM

My '68 had the 3/4" on top and ran to the water pump.

**DeadheadNM** · 05-31-2022, 09:02 AM

See here: http://67-72chevytrucks.com/vboard/s...99&postcount=3

**tjc** · 05-31-2022, 09:07 AM

Does anybody run their heater hose to radiator like the manual shows for auto transmissions ?

BASE · 05-31-2022, 09:23 AM

Quote:

Originally Posted by tjc

Does anybody run their heater hose to radiator like the manual shows for auto transmissions ?

Some discussion on that in the rest of the thread DeadheadNM linked above. If I had a radiator with the 3/4" fitting on it, I'd just use it and put a plug in the pump. Otherwise, they seem to work just fine for me with the return going to the pump.

geezer#99 · 05-31-2022, 10:20 AM

Quote:

Originally Posted by tjc

Does anybody run their heater hose to radiator like the manual shows for auto transmissions ?

I have but only because the rad I was using had the bung on the rad. Not an easy fix to remove it or cap it so it doesn’t leak.

**tjc** · 05-31-2022, 05:42 PM

So the 3/4 inlet on top of heater core is the return line back to water pump or radiator. You would think the water would enter the heater core at the top not the bottom.

**Stocker** · 05-31-2022, 06:11 PM

No, since heat rises, the hot (inlet) to the heater core is at the bottom. The top (outlet) goes to the radiator to be recirculated.

I know some trucks are routed differently, but the heater core should always be inlet at the bottom, outlet at the top.

Found this in a prior search:

Quote:

Automatic and A/C trucks returned to the radiator for better overall cooling and base trucks returned to the pump for quicker warmup.

PbFut · 05-31-2022, 07:56 PM

Water supply to bottom of core. This so any air in the core wanting to "float" will be easily removed with the return coolant back to the radiator. This also helps eliminate hot spot in the heads during warm up when tstat is still closed, assuming the AC is not the position that closes the flow valve. Since there is always flow you avoid hot spots in the heads which also protects head gasket. Those without a core should still accommodate coolant flow in some manner to retain the factory intended protections

**DeadheadNM** · 05-31-2022, 08:36 PM

Quote:

Originally Posted by tjc

Does anybody run their heater hose to radiator like the manual shows for auto transmissions ?

Yes both my trucks but these are also AC equipped.

05-31-2022, 08:44 AM	#1
tjc Senior Member Join Date: Jun 2011 Location: burlington,iowa Posts: 438	heater hose placement I have seen it done in both directions, 68 c10 with 350 non air truck. Heater core 3/4 fitting at top and 5/8 on bottom. from the water pump to the heater core, top or bottom? __________________ Tom in Iowa 68 L88 C10 68 4x4 C10 soon

05-31-2022, 08:53 AM	#2
BASE Registered User Join Date: Oct 2016 Location: St Louis, MO Posts: 194	Re: heater hose placement My '68 had the 3/4" on top and ran to the water pump. Attached Images __________________ __________________ '68 K10 496/465/205

05-31-2022, 09:02 AM	#3
DeadheadNM Carpe manana Join Date: Dec 2010 Location: Eau Claire, WI Posts: 12,308	Re: heater hose placement See here: http://67-72chevytrucks.com/vboard/s...99&postcount=3 __________________ 1972 K5 CST Highlander Blazer: http://67-72chevytrucks.com/vboard/s...d.php?t=708547 1972 K20 Cheyenne Super: http://67-72chevytrucks.com/vboard/s...d.php?t=528308 Members met: ORANGBLAZ, 2003 silverado, MikeCofield, BB72CHEVKT, Duncan&Son, Sameyrasmea72, THENEWMEXICAN, HotRod C/10, brianthelion02, Sport/Truck, ryanroo, michael bustamante, Dirt's72, Already Gone, WestButteTruck, 57taskforce, Moreyel, painterljp, AASmedic, SoCoC10, Lumaestas, carbuff382, Chevyland

05-31-2022, 09:07 AM	#4
tjc Senior Member Join Date: Jun 2011 Location: burlington,iowa Posts: 438	Re: heater hose placement Does anybody run their heater hose to radiator like the manual shows for auto transmissions ? __________________ Tom in Iowa 68 L88 C10 68 4x4 C10 soon

05-31-2022, 05:42 PM	#7
tjc Senior Member Join Date: Jun 2011 Location: burlington,iowa Posts: 438	Re: heater hose placement So the 3/4 inlet on top of heater core is the return line back to water pump or radiator. You would think the water would enter the heater core at the top not the bottom. __________________ Tom in Iowa 68 L88 C10 68 4x4 C10 soon

05-31-2022, 07:56 PM	#9
PbFut Registered User Join Date: Feb 2022 Location: Ca Posts: 415	Re: heater hose placement Water supply to bottom of core. This so any air in the core wanting to "float" will be easily removed with the return coolant back to the radiator. This also helps eliminate hot spot in the heads during warm up when tstat is still closed, assuming the AC is not the position that closes the flow valve. Since there is always flow you avoid hot spots in the heads which also protects head gasket. Those without a core should still accommodate coolant flow in some manner to retain the factory intended protections



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