Great info here, thanks everyone. Im going to try go with the expansion tank route. Just one thing Im wondering about.
When filling a system like this with a cross flow radiator from empty you wont be able to fill the radiator 100%. There might be around 1" of air left at the top. Will the rest of the coolant expand enough to push this air out and later suck coolant back from the reservoir and fill the radiator 100%?
Maybe its not that important, its a big rad for a pretty mild 360. Any thoughts?
