About that ball/spring thing ... it's function is still not clear to me, but
.... it's purpose seems to be to balance the cold water bypass to the 2 sides
of the (e.g. my V6) engine. There's a pic of it ... it's at the top of the
lower (bottom) diagram ... Warm Manifold System. So if one manifold is cold,
maybe the thermostat is not opening as soon as it should (engine is actually
overheating) and cold water is being directed more to one manifold (by the
tee valve assembly) rather than to both?

The link ...
http://www.perfprotech.com/home/tech...oling-tips.htm

Hey, just thinking out loud here :-)

In my V6, there's a ball/spring mechanism in the cooling system that I
come
across every fall when I pull all the water lines for draining/winter
storeage. I've just now looked through my Seloc manual, and don't see it.
It
may have something to do with controlling water flow to each manifold ...