if the system was sealed the recovery container would have the same positive and negative pressures as the rad and engine [which use a 14# cap or higher], I doubt the usual plastic reservoirs would stand that, let alone a mason jar [as John explains]
I'm pretty sure Weeds is running a 283, and states he has a 7# cap, a 283 with a 7# cap shouldn't normally run much over the thermostat rating, so will not generate the temps and pressures necessary to make a modern style recovery system function, it needs the more extreme contraction to draw the water back from the tank
283's blowing off a bit has been the subject of threads here before, and it's invariably a situation of filling the rad to the top when cold instead of leaving enough head space for expansion .... I'm sure if the bottle were emptied
without topping off the rad, it wouldn't "flow coolant into the bottle" again
Bill
