I would add as many as about a pint or so of distilled drinking water.. any more and I'd pick up some coolant To combine. if it goes off again, convey it to your vendor. its probably just evap lack of the drinking water part of the coolant blend. glycol https://electrical-mechanic-near20530.luwebs.com/27844873/5-simple-techniques-for-types-of-coolant-for-bmw-335i