...
-New 3 core all brass radiator (realize not the conductivity of Al, but can't be that bad).
...
Oh yes,
it really can be that bad. It was for me, and many others as well.
Specifically, the CSF 2517 all brass is a known poor performer, by many people.
(but oddly, not all, but go ahead and waste your time with it if you want to)
Read all about it
here. Or search - all this has been
Known best performers:
TYC 1918 - cheap aluminum / plastic. (
www.rockauto.com, $131 shipped when I did it)
OEM - medium priced aluminum / plastic.
Ron Davis - very expensive, top shelf quality, TIG welded aluminum.
And, BTW, regarding the water pump.
There's nothing to it - nothing to "go bad" that wouldn't be glaringly obvious to the casual observer.
It's not a subtle device.
It's just a whirly thing on a shaft, bearing, housing.
If the whirly thing is still there (hasn't corroded down to nothingness), and the bearing still turns smoothly - well, what else is there?