Firstly, only fill the coolant when the engine is cold, 1st thing in the morning, the reason it all came out of the expansion tank is its a pressurised system.
So fill it up from cold, with the ignition on pos II, put the air con on at full HEAT but LOWEST fan setting, and bleed the system, then start it up bleed with the cap on and bleed, it may take a couple of days to get the level correct, but only check and fill when cold.
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