Heater core shut off valve

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Hey everyone!
I read somewhere on here that someone had put a valve on their heater core inlet hose. So that the hot water would not circulate in the heater core.
I'm interested in this fix as summer approaches.
My heater shut off is worn out and allows hot air into the cab all the time.

My question: Will adding a valve in my system cause any problems?
Any advice is much appreciated.