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#1 |
Registered User
Join Date: May 2000
Location: Middletown, Ohio
Posts: 131
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Heater Hose Tube on Radiator
Getting ready to install new heater hoses on my Longhorn 402 big-block. Truck has no A/C correct factory heater box on firewall with 3/4" core tube on top and 5/8" core tube on bottom.
I have the normal 5/8" fitting on top of engine manifold near thermostat housing. This supplies hot water into the bottom of heater core. I have the normal 3/4" fitting for a return from the top of the heater core to the side of the water pump. Any ideas why my radiator has 3/4" Male Heater Hose Tube about an inch below filler neck pointing straight out toward engine? Maybe it's for an auxiliary heater return or something?? I can't think of any purpose for it. Maybe somebody knows or has seen it on other trucks. |
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#2 |
20' Daredevil (Ret)
![]() Join Date: May 2003
Location: Jefferson State
Posts: 13,634
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Re: Heater Hose Tube on Radiator
IIRC, the preferred routing for the 3/4" return hose is to the port on the radiator -- not to the water pump.
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- Mike - 1972 K20 LWB 350/350/205 RIP El Jay |
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#3 |
Registered User
Join Date: May 2011
Location: Syracuse, Utah
Posts: 1,930
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Re: Heater Hose Tube on Radiator
Take a look at this thread http://67-72chevytrucks.com/vboard/s...d.php?t=188679
Here is another pic from the 1972 Chevrolet Truck Chassis Service Manual 10 to 30 (1A-3). I have the same HD Rad in one of my C30's it's non-A/C with Turbo 400. Hope that helps.
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Brett ![]() 67 Camaro SS Build:http://67-72chevytrucks.com/vboard/s...d.php?t=751594 72 Cheyenne/10 Super 115" Fleetside (Waiting it's turn.) 72 Cheyenne/K30 Super 133" DRW SOLD Build:http://67-72chevytrucks.com/vboard/s...d.php?t=645614 YouTube: https://www.youtube.com/@6dee7-7dee2 |
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#4 |
Registered User
Join Date: May 2000
Location: Middletown, Ohio
Posts: 131
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Re: Heater Hose Tube on Radiator
O.K., thanks alot.
Found the pictures in my Factory Service Manual Section 1A. I'm going with the 3/4" return to the radiator. |
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#5 |
Registered User
Join Date: May 2011
Location: Syracuse, Utah
Posts: 1,930
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Re: Heater Hose Tube on Radiator
No problem, I have not had any issues running my truck this way.
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Brett ![]() 67 Camaro SS Build:http://67-72chevytrucks.com/vboard/s...d.php?t=751594 72 Cheyenne/10 Super 115" Fleetside (Waiting it's turn.) 72 Cheyenne/K30 Super 133" DRW SOLD Build:http://67-72chevytrucks.com/vboard/s...d.php?t=645614 YouTube: https://www.youtube.com/@6dee7-7dee2 |
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#6 |
Senior Member
![]() Join Date: May 2010
Location: Wisconsin & Arizona
Posts: 4,844
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Re: Heater Hose Tube on Radiator
Just to clarify the hose routing...
Based on my observations, the earlier model year trucks had the 5/8" hose from the heater core to the intake and the 3/4" hose to the side of the water pump. There was no 3/4" fitting on the radiator. I'm not sure when the change actually occurred. My 69 with a 350, A/C and 4 row radiator is routed this way. All, or most, of the later year trucks (71/72?) I've seen had the 3/4" hose to the radiator. |
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#7 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: Heater Hose Tube on Radiator
I've been working on GM cars and trucks for along time and I've NEVER seen a heater hose go directly to the radiator. I almost looked to see if it was April 1.
You learn something every day. Why only with automatic trans? It looks like hot water comes out of the engine, goes to the heater core, and dumps back into the radiator. I would think this would really slow down engine warmup...
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#8 | |
Registered User
Join Date: Mar 2012
Location: New Orleans, La
Posts: 406
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Re: Heater Hose Tube on Radiator
Quote:
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It's not that I am apathetic, I just don't care. If your life is a joke, it appears death will be your punchline. |
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#9 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: Heater Hose Tube on Radiator
I wasn't thinking of heat loss through the heater core as much as the fact that it would be continually cycling its warm coolant through the core and back out to the rad rather than keeping it in the engine. So I see it as not having a thermostat but with a smaller rad hose, in a way.
A "normal" configuration would send it through the heater core and back to the engine for further warming (or re-warming). Once the thermostat is open and all the coolant is at operating temp, shouldn't make a diff.
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#10 | |
20' Daredevil (Ret)
![]() Join Date: May 2003
Location: Jefferson State
Posts: 13,634
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Re: Heater Hose Tube on Radiator
Quote:
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- Mike - 1972 K20 LWB 350/350/205 RIP El Jay |
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#11 |
Registered User
Join Date: Jan 2000
Location: Wyoming USA
Posts: 2,445
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Re: Heater Hose Tube on Radiator
OK got a ? for you all ,it seems to me that it would cool down the system better if it went to the radiator.Is there any logic to this ,I have a/c cab(someday I'll hook it all up) but man does it get heat from the heater core.Even when I just try and get outside vent air
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2001 Silverado K-1500 2005 FXDWG stage3 69 CHEVY Short/Step 327/4L60 373 posi 63 IMPALA 327 |
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#12 |
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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Here is the heater hoses in the factory manual for AC.
I agree if the hose on the water pump pumps water through the heater core and dumps straight back to the radiator it would take longer to heat up the truck to correct temp. The hot engine water going through the heater want cool it down much and dumping back straight to the radiator will not let the engine water temp get hot very quickly because it's cooling off with out building heat up in the system. How long does it take for the truck heater to warm up the truck on cold days? That would be the test to perform and see if there is enough differance in the heat to change it. ![]() ![]()
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1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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#13 |
Chemist under the hood...
Join Date: Apr 2009
Location: Fort Erie,ON, Canada
Posts: 617
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Re: Heater Hose Tube on Radiator
This is the same issue I'm having so instead of posting another thread, I'll just add on. I had the 3/4" line on the rad capped with a rubber end cap and hose clamp. My setup was 5/8" line from intake to bottom of heater core, 3/4" line from top of heater core to fitting on water pump.
Yesterday, my rubber rad cap failed, spewing coolant in the parking lot so I started to look to see if I could fix this setup. What do people think about capping off the water pump inlet and letting the heater core go to the rad fitting? The 3/4" hose fitting on the water pump doesn't look like it will come off easy so putting the plug on it may mean taking the water pump off. Is there any advantage having the heater return to the rad instead of the pump? I have a 283 with no A/C and manual trans. Thanks!
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Current fleet: 2013 GMC Sierra, 5.3L, 4x4 1988 GMC Sierra, 305, Auto 1984 Jeep Grand Wagoneer, 360 V8 1997 VW Cabrio, 2.0L 2017 Toyota Rav4, 2.5L Stuff I wish I still had: 2013 Toyota Matrix [RIP] 1967 GMC 910 Fleetside, 283 V8 [1st Love-SOLD] 1987 Jeep Cherokee Laredo 4X4, 4.0 I-6 [SOLD} 1994 Chevrolet Caprice Classic, 5.7LV8 [SOLD] 1995 Chevrolet Astro AWD, 4.3L V6 (RIP) 1998 Chevrolet Suburban 4x4, 5.7L V8 [SOLD] |
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#14 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: Heater Hose Tube on Radiator
The LMC rad I bought for my '70 had this port. The factory one didn't so its another case of a 'halfway universal' reproduction part.
Mine leaked badly. I wound up having to pull the rad out, put a metal plug in, and solder it up.
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#15 | |
Account Suspended
Join Date: Jan 2007
Location: Tucson
Posts: 2,183
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Re: Heater Hose Tube on Radiator
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#16 | |
Chemist under the hood...
Join Date: Apr 2009
Location: Fort Erie,ON, Canada
Posts: 617
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Re: Heater Hose Tube on Radiator
Quote:
I wonder if a T fitting would work? That way some would return to rad and some to water pump?
__________________
Current fleet: 2013 GMC Sierra, 5.3L, 4x4 1988 GMC Sierra, 305, Auto 1984 Jeep Grand Wagoneer, 360 V8 1997 VW Cabrio, 2.0L 2017 Toyota Rav4, 2.5L Stuff I wish I still had: 2013 Toyota Matrix [RIP] 1967 GMC 910 Fleetside, 283 V8 [1st Love-SOLD] 1987 Jeep Cherokee Laredo 4X4, 4.0 I-6 [SOLD} 1994 Chevrolet Caprice Classic, 5.7LV8 [SOLD] 1995 Chevrolet Astro AWD, 4.3L V6 (RIP) 1998 Chevrolet Suburban 4x4, 5.7L V8 [SOLD] |
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