Simple heater question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Jakes-66-K10 · 05-31-2005, 05:17 PM

As dumb as it sounds, I just want to make sure I have my heater hoses hooked up right. Which hose goes into the intake manifold, upper or lower?

R@nger · 05-31-2005, 06:10 PM

I believe its the bottom to intake manifold and the top to the top of the radiator.

Jakes-66-K10 · 05-31-2005, 06:33 PM

you mean water pump? heater hose shouldn't go to radiator...

Longhorn Man · 05-31-2005, 06:35 PM

some go to the rad, some go to the pump, and it makes no difference at all which is top and which is bottom.

Jakes-66-K10 · 05-31-2005, 06:39 PM

wha-what? really.... hmm

**john** · 05-31-2005, 06:43 PM

The lower heater inlet is 3/4" and goes to the intake, the upper 5/8" goes to pump or rad. The water circulates from bottom to top of heater core. John
EDIT CORRECTION after reading meangreen post I realized I had my head you know where. Thr 5/8 goes to man, 3/4 to pump.

John

R@nger · 05-31-2005, 08:08 PM

Oh well I learned something new today. I didn't know there was a pump option. Sorry if that confused ya vortex, thats just the way mine is set up on my 71 gmc.

By the way where in Utah are you?

71meangreenc10 · 06-01-2005, 08:25 AM

My pump has the 3/4 on it and the manifold has the 5/8, so mine runs top to manifold and the bottom to pump. Works great so far....

Longhorn Man · 06-01-2005, 07:44 PM

exactly...it doesn't matter one bit.

chipflyer · 06-01-2005, 10:10 PM

The hottest water in the engine will come out of the top of the engine (5/8 intake fitting) and goes into the bottom of the heater core 5/8 fitting. After circulating through the heater core water returns out of the top heater core line which is 3/4 and returns back into either the water pump or radiator.
It will work if hooked up backwards just not as well and its wrong. There is a reason the fittings are a different size, heat always rises, and return lines are always bigger whether your talking about hydraulics, A/C, or heating systems.

Jeff

**Green Machine** · 06-02-2005, 12:10 AM

I agree with chipflyer, and I might add that any air bubbles present in the heater core are more likely to get flushed out with the coolant circulating from the bottom in and out the top.

05-31-2005, 05:17 PM	#1
Jakes-66-K10 Registered User Join Date: Aug 2004 Location: Idaho Posts: 640	Simple heater question As dumb as it sounds, I just want to make sure I have my heater hoses hooked up right. Which hose goes into the intake manifold, upper or lower?

05-31-2005, 06:10 PM	#2
R@nger Psalm 23 Join Date: Apr 2005 Location: Utah Posts: 360	I believe its the bottom to intake manifold and the top to the top of the radiator. __________________ 71 GMC Fleetside C15(cab), 3/4 ton, 350, Holley Street Avenger 570cfm carb, TH350 trans, Leaf-springs, 2WD. "Peter are you sleeping on the job? No I have a bug in my eye and I'm trying to suffocate him." - Family Guy

05-31-2005, 06:43 PM	#6
john member #16 Join Date: Dec 1999 Location: Yuba City Ca. Posts: 3,618	The lower heater inlet is 3/4" and goes to the intake, the upper 5/8" goes to pump or rad. The water circulates from bottom to top of heater core. John EDIT CORRECTION after reading meangreen post I realized I had my head you know where. Thr 5/8 goes to man, 3/4 to pump. John __________________ john http://67-72chevytrucks.com/vboard/showgroups.php board vendors http://www.flickr.com/photos/1745471...7602865984234/ Last edited by john; 06-01-2005 at 04:09 PM.

05-31-2005, 08:08 PM	#7
R@nger Psalm 23 Join Date: Apr 2005 Location: Utah Posts: 360	Oh well I learned something new today. I didn't know there was a pump option. Sorry if that confused ya vortex, thats just the way mine is set up on my 71 gmc. By the way where in Utah are you? __________________ 71 GMC Fleetside C15(cab), 3/4 ton, 350, Holley Street Avenger 570cfm carb, TH350 trans, Leaf-springs, 2WD. "Peter are you sleeping on the job? No I have a bug in my eye and I'm trying to suffocate him." - Family Guy

06-01-2005, 08:25 AM	#8
71meangreenc10 Its a Truck Thing...... Join Date: Dec 2004 Location: Sierra Vista, Arizona Posts: 3,159	My pump has the 3/4 on it and the manifold has the 5/8, so mine runs top to manifold and the bottom to pump. Works great so far.... __________________ 71 C10 283/3SPD Full Resto 71 GMC 1500 Sierra Grande http://67-72chevytrucks.com/vboard/s...d.php?t=518599 70 C10 Suburban Former military GSA truck. 72 Chevy Blazer 4X4, Sloppy Jo, Mountain Climber. Wife says no more trucks. http://67-72chevytrucks.com/vboard/s...d.php?t=707378 72 GMC 1 Ton Motor Home, wife said no more trucks until she saw this one. Gen 3 6.0/4L80E 4.10 http://67-72chevytrucks.com/vboard/s...d.php?t=761110 68 GMC Suburban was 3/4 ton, now 1/2.Wife shook her head 71 C30 Wrecker 71 C20 Scott-Bilt As weird as it gets..BB Cheyenne AC Truck 68 GMC Long Stepside. They keep following me home 71 C20 Longhorn/Ole Yellor 69 C30 Former Motor Home, Flat Bed time

05-31-2005, 06:33 PM	#3
Jakes-66-K10 Registered User Join Date: Aug 2004 Location: Idaho Posts: 640	you mean water pump? heater hose shouldn't go to radiator...

05-31-2005, 06:35 PM	#4
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	some go to the rad, some go to the pump, and it makes no difference at all which is top and which is bottom.

05-31-2005, 06:39 PM	#5
Jakes-66-K10 Registered User Join Date: Aug 2004 Location: Idaho Posts: 640	wha-what? really.... hmm

06-01-2005, 07:44 PM	#9
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	exactly...it doesn't matter one bit.

06-01-2005, 10:10 PM	#10
chipflyer Registered User Join Date: May 2004 Location: Topeka, Ks Posts: 2,293	The hottest water in the engine will come out of the top of the engine (5/8 intake fitting) and goes into the bottom of the heater core 5/8 fitting. After circulating through the heater core water returns out of the top heater core line which is 3/4 and returns back into either the water pump or radiator. It will work if hooked up backwards just not as well and its wrong. There is a reason the fittings are a different size, heat always rises, and return lines are always bigger whether your talking about hydraulics, A/C, or heating systems. Jeff __________________ I'm not a pessimist, I'm just optimistic that bad things are going to happen. 1971 Cheyenne Super K10 - tilt, cruise, air, am/fm, tow hooks, factory buckets! 1986 Jeep J10 pickup, - 5.3L Vortec with 4L60e and NP241.

06-02-2005, 12:10 AM	#11
Green Machine Senior Member Join Date: Jul 2004 Location: Estherville, Iowa Posts: 3,371	I agree with chipflyer, and I might add that any air bubbles present in the heater core are more likely to get flushed out with the coolant circulating from the bottom in and out the top. __________________ 1968 C10 307 3spd Long Fleet ------ http://67-72chevytrucks.com/vboard/s...d.php?t=201103 1970 C10 305 Super T10 Long Fleet --- http://67-72chevytrucks.com/vboard/s...d.php?t=202285 1971 C20 383 TH350 Dana Posi ----- http://67-72chevytrucks.com/vboard/s...d.php?t=206894 2001 GMC Sierra 1500 C3 6.0



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