When I got my truck, someone had put these "red" heater hoses on it. They worked Ok, but the one on the bottom of the heater valve is supposed to be 1/2" line from the intake manifold to the heater valve. All the others were 5/8". The one that was to big hose kept leaking in different ambient temps. So I put the correct hoses on today. I think it looks a whole lot better. I have a question though. Why is the hose coming from the intake nipple to the heater valve 1/2" anyway? On the other side of the valve it is 5'8" to the heater core tube. Something to do with slowing the water down to get better heat to the heater core?
Anyone
The old hoses.

The new ones.