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Radiator stays hot when closed.
So I just moved into an apartment building that uses old cast iron radiators. there is only one valve on the left of the radiator that says 'open' with an arrow going counter clockwise. It had got really cold, naturally being in Canada, so I opened the valve to fill up with hot water. I closed the valve after 30 sec and it is still very hot after weeks of initially opening it. Now, the radiator in my bedroom, is boiling hot on the right side and warm on the left where the valve is, of which I have never opened. How do I turn the heat off, I can't sleep because it's a thousand degrees!