The most recent one was the guy complaining about the design of his heater core..
Heat dropped at idle. "Without" overheating. And hasn't posted since water pump replacement.......gunna go with there's your example..
He also had "no" coolant loss.
I've had the same condition with mine. No coolant loss. Freezing temps at stops. Never overheated. Water pump fixed it.
Pretty sure CzarKJ just had a similar condition that was fixed by a water pump.
That's three very recent examples.. so sorry you haven't experienced this in 20+ years.
perhaps to you these don't seem relevant to the current post, but it's not like we said yes, definitely your water pump and couldn't be anything else.
But if you look, he didn't mention coolant loss in the first post. Nor did he mention overheating..