2015 Promaster 2500 Diesel “vacuum coolant valve”

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Hello, I hope I’m in the right place.
I have a 2015 Promaster 2500 Diesel. I was told by the dealer that I need a new “vacuum coolant valve” but I can’t find any reference to that part? Does it have a different name for my van that would help me find it?
The reason I ask is because I took it in for a coolant leak. I could see it was coming from the lower radiator hose so I expected they would tell me that it needed replacing. But there were no other problems. Heater works fine and it wasn’t overheating. Just the leak.