I'd increase up to a couple of pint or so of distilled h2o.. anymore and I'd pick up some coolant to mix. if it goes off yet again, convey it on the supplier. its likely just evap lack of the drinking water part of the coolant mix. glycol doesnt evap https://archerakjmm.isblog.net/5-easy-facts-about-types-of-coolant-for-bmw-335i-described-44406871