Any Harm in Cutting Off Heater Core Flow?

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I would like to turn off the flow through the heater core in the summer. Reason? Some heater cores fail from erosion caused by coolant flow. The ball valve with the red handle, which I added when I installed a coolant filter, will enable me to shut off the flow. Heat regulation in the cab is through an air flow door, there is no coolant valve regulating temperature. The 4.3 in my truck has a bypass hose from the stat housing to the water pump. So I think the core isn't needed for bypass purposes.
 
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There must always be flow through the engine and it must pass near/over the thermostat or the thermostat may open to late. Usually this flow is through the heater core but the "bypass" you talk about might be doing this for you. I had a car with a plugged heater core and the temp would oscillate up and down. Unplugging the heater core cured the problem. I can't see any harm in what your are trying. Just keep an eye on it.
 
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Being that you have a separate bypass to maintain flow when the t-stat is closed, blocking the heater circuit shouldn't hurt anything. It's only an issue on engines where the heater circuit is the only bypass flow.
 

George7941

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The climate control in my truck is about as non-automatic as you can get - both the temperature door and the mode door are operated by old fashioned cables.
 
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Originally Posted By: George7941
The climate control in my truck is about as non-automatic as you can get - both the temperature door and the mode door are operated by old fashioned cables.
I saw a figure recently which claimed that over 50% of new cars come with the automatic version. We don't those folks shutting off the flow. I like the "armstrong" method myself, but, like automatic transmissions, it will be increasingly harder to find.
 
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Just put a blanking plate during the winter over the radiator. Cheap, reliable and it works. The only way to prevent a heater core from rotting is to use the correct OEM coolant in winter. If not, then see if you can find some soluble oil in a marine store, as that is a real good antioxidant. You just add a small quantity to distilled water and it turns into coffee cream mix, BUT is no good below 0c.
 
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Some GM cars has a real problem with the heater cores so its best to take them out of the loop in the summer. Using a loop hose takes the core out for good unless you connect the hoses again. The point of using a bypass valve is to give you control over it when its needed. On mine I use an electric vacuum switch, off and its flowing through the core as usual so you can get defrost and some heat if needed, on and its in bypass. Some old cars used them with just a winter/summer lever, others used a cable. Many manufacturers use them today it can help A/C performance.
 
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