I had this, maybe you can find similarities:

- overflow of coolant from the hose of the radiator
- the reservoir was filled up, but the radiator empty. Can you check the level in the radiator?
- engine overheat turned on. Just continuously filled up the radiator and could drive another 400km.

Solution: the spring of the cap of the radiator was too weak. So couldn't hold pressure and lowered boiling temp of the coolant.
So, got myself an new spring and put it in the cap. Never lost another drop.