[64cabro]

Thanks for the suggestions Tom, JSchmitz.

Dad put 500 miles on the odometer after finishing the restoration, and I've put about 500 on it. Total rebuild of the engine by an engine guru near home, so the coolant is "old" (2016) but not very used (mileage). Based on that guru's reputations, I'm willing to assume that the water pump impeller clearance is correct as I've read that can cause poor flow. The radiator is filled up just enough to cover the core, so I know there's at least plenty of coolant in there. I'll start with testing the temp sensor and maybe the t-stat. Flushing the cooling system wouldn't be that hard for me either if it might help.

How important is a 50:50 mix of coolant and water to the cooling performance?

Does the age of the coolant (going on 5 years now easily) make a difference?