1993 Other Peugeot Models Water formation inside Tapitt cove

I added a water reservoir bottle to my peugot engine radiator outflow. The engine cooling system did not have one. Instead it had normal water outlet pipe.

Recently water formation inside tapitt cover was detected.

After varification with your engineers that the head and the gasket were OK, I have another query that - can adding a water reservoir bottle to the radiator that does not have a water ouverflow pipe, be causing water formation inside the tapit cover?