There's no separate connection on my Rad for the feed from the header tank so where's the best place to plumb it into? Do I tee into the Rad outlet or return line?

I worked on the theory that if you take it from the highest point, then as the water expands,
any air in the system will be forced out. For me it was the thermostat housing, which I drilled
and tapped and ran a small bore pipe to the bottom of the header tank.
On cooling, water should be sucked back into the system.

This works for my Lotus engine, but can't think why it shouldn't work on all engines.

Hth

Paul G