Seems I'm running into bigger trouble:
I'm not happy.
Yesterday evening I had filled up the cooling system.
Today morning I found the coolant tank empty.
I've filled it up again (3L) and I saw a small leak on the left engine side where the chain housing meets the block.
I tried to block the leak with silicone and left it like this for the day.
This evening the coolant tank was empty again but no puddle of water on the floor.
Tomorrow I'll open the drain plug of the oil pan and see if there comes any water out.
Maybe the system leaks to the inside.
Not good engineered engine to have water and oil side by side, just seperated by a simple paper gasket.