Light cooling water consumption at the 850 TDI

Hello everybody, I’m new here and need a little help: I’ve had a Volvo 850 Tdi for some time now, with about 304 000 km on the clock. After having completed some holiday trips to Denmark and southern Italy without any problems in summer, one day after I drove a distance of about 800 km, a large pool under the car!!! Tasted, and fed, that tastes like cooling water… afterwards there were rarely even smaller spots under it, now it has completely stopped! Trozdem regularly disappears water from the balance tank, currently about 0.3 liters to 1000 km. A workshop has pressed the system and said, all close enough, the master then said that because of the high mileage the engine is already a little “exploded” and therefore a coolant consumption of up to 0.3 liters to 1000 km is tolerable. Bubbles are not available in the container, in the oil is no water and vice versa, after starting it smokes a little white from the exhaust, but when it is operating warm no longer. Ride in the moment a lot short distance between 7 and 30 km… Does anyone know the problem?