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On my 79 which heater hose is the inlet and which is the outlet. Which hose feeds coolant to the heater core and which exits coolant from the core? I don't have a vacuum hot water shut off valve on it and I am think to putting some type of shut off on it again. My intent is to cut off fluid to the heater core and stop pressure on one or both lines if possible.
Joe
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I just capped mine off at the water pump yesterday, $2.00 and just tucked the heaterhose into the fender beside the a/c compressor. Works great and easy to install and remove (best of all cheap)
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The one going to water pump is the outlet or return. Most guy's will put shut-off on both hoses.
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It really does not matter which hose you put the valve on. If you stop the water flow in or out, you also stop the other one. No flow is no flow.
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r
Mine made no difference at all until I put valves on both hoses. Even if the hot water is not moving, it is still in the heater core. That heat will still infiltrate the corkpit. On most of the threads posted. most people valved both heater hoses. Again, putting one valve on mine made little to no difference. When I did both, it made a huge difference. I hope this helps. I hope someone else chimes in.
Scott
ranger3 2008-07-14 18:09:57
Scott
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With one there is no flow. If two helped, it had to block heat radiating through the non flowing water. Possible. I have only one and it works fine.
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Send PMCramerton, NC - USA
Joined: 8/22/2006
Posts: 1094
Vette(s): black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion
Here is an old thread on the same topic. Seems its a "HOT" topic every summer 
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Thanks for the inputs. It appears the hoses may have been two different sizes? 3/4 and 5/8? I also discovered last night in my assembly manual there is a tube inline under the a/c bracket for the lower hose coming off the water pump. I need to get it, just running the a hose right now. I had a valve on it at one time, but it always got corroded and had to be replaced.
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K
I've been reading many of these threads about installing heater hose shutoff valves. Sounds like a good idea.
I'd like to go ahead and get this done & I'll be using 2 valves - 1 on each heater hose.
(How am I doin' so far?)
My qeustions are;
1) If I install both valves and run the engine, should I first shut one valve off to block any further coolant from entering the heater core?
2) Then, would leaving the other one opened for a time evacuate what coolant is left in the heater core. At some point I'll know the heater core is empty (I hope) and then I'd close the second valve. I'm thinking that an empty heater core is what I'm after to keep things cooler.
3) If I'm on the right track here, does an empty heater core rot out or cause other problems?
I hope I'm not overcomplicating an easy job. 
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Just to throw this out there, I have made sure my sytem is working properly.(new vacum valve and testing that vacum is there to shutoff the valve. I was wondering if placing onother vacum valve on the other hose would make a differance.
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in Forum: C3 HVAC, Fuel, Emissions, and Exhaust
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