water circulation question

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kiss

kiss

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I have a question on how water circulation works on our Mopars. The car is a 71 Dart non A/C. I am doing a radiator flush. Question--- do I need the heater ON to have warm water circulate through the heater core? I was under the impression since there's no shutoff valve on the heater lines that water is always circulating through the heater core in our cars. The only thing the controls do is open/close the air access vents.
 
Your correct in your thinking. To reinforce it, just feel the 2 hoses going into the heater. On my 71 cuda i put a shutoff valve in the hose going to the heater so I wouldn't get any hot air at all. I used a ball valve to shut it for summer and open it in winter.
 
kiss...

i would offer a thought to "shutting off" the water flow through the heater core. water flowing through a heater core does provide some additional cooling of the engine water. that is why you can often turn the heater on in a car that is overheating and gain enough driving miles to get the car home or to a gas station. as old mopars were designed to have the water flowing through the heater core at all times, you might find the car running a little hotter if you block this flow. if your radiator is good, you probably won't notice any temperature rise. however, if you do, it may be as a result of you stopping water flowing through the heater core.
 
Your thought has some merit but all A/C cars shut off heater core when in operation. They would especially need that little bit of extra heat removal if it was efficient, especially when pumping freon to cool passengers.
 
You would not believe how much cooler the interior is on hot days with that heater core taken out of the circuit. That core adds a ton of heat to the interior, right when you don't need it.
 
When mine was together, I simply put a 3/8 1/4 turn ball valve with 3/8 pipe nipples in one hose. 3/8 pipe is the perfect size for 5/8 heater hose.

If this was the 70's-80's when we had "real" parts stores with "real" catalogues, you could look through the "picture book" (pictorial guide" and find all kinds of interesting doo--dads, including cable operated manual valves, etc.
 
back to the subject of flushing... Water flows through the heater core in one direction. Crap collects in there, sticks and stays. Wanna see for yourself... Take the 2 hoses off at the engine ends and drape them over the right fender. Garden hose flush in one direction until the water flows pretty much clear. Now switch the garden hose, flow opposite direction. You'll do this a few times before it runs clear both ways. Come winter time the heater should perform much better. Be aware, If its the OEM heater core it might start leaking. Chit happens when we disturb old plumbing in any case. Good luck
 
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