I might add nearly a few pint or so of distilled water.. any more and I'd get some coolant to mix. if it goes off once more, provide it to your seller. its probably just evap lack of the drinking water percentage of the coolant blend. glycol doesnt evap as https://reliable-mechanics-near-m40593.spintheblog.com/27651219/the-5-second-trick-for-types-of-coolant-for-bmw-335i