I would include approximately a couple of pint or so of distilled water.. any more and I might pick up some coolant to mix. if it goes off once more, convey it on the dealer. its likely just evap loss of the drinking water part of the coolant blend. glycol https://brakeservicecoralridgeisl96370.blognody.com/26893853/detailed-notes-on-types-of-coolant-for-bmw-335i