cooling question

what purpose does the overflow recovery bottle serve on the closed system other than a place to add fluid?
what if ?? the 2 lines going to the tank were coupled together?
would the fluid that normally gets puked into the jug just go right back into the sytem?
just trying to understand the concept/ flow of things on this newly aquired xj.
does a "normal" operating 87 xj cooling system have a continuous flow of coolant cycling thru that recovery tank at any given time?

That pressure turtle is for expansion, open systems expand into the overflow tanks than as the coolant contracts the system sucks it back in. On the closed system it just pressurizes. We had a 61 Ford 352 country squire that had a closed system, the expansion tank was a steel one mounted over the intake manifold of that V8 and used big normal hoses and a normal rad cap, it did however just vent to the ground it was also however directly in the path of the fan so it got some cooling from that.