I'd insert as much as a few pint or so of distilled water.. any more and I'd pick up some coolant to mix. if it goes off once more, provide it to the dealer. its possible just evap lack of the h2o percentage of the coolant combine. glycol doesnt evap https://rafaelbkrxc.life3dblog.com/26835056/an-unbiased-view-of-types-of-coolant-for-bmw-335i