coolant overflow problem

Hello all. new member here. I have an 88 e28 and I'm having a coolant overflow problem. I recently changed the thermostat and water pump. I'm having coolant discharge from the overflow tube although the temperature while running registers fine. I bled the air before filling with coolant. Any ideas? Thank you.

Replace the coolant tank cap. Cheap and easy fix. If that's not it you might have a bad head gasket pressurizing your system (guess why I know that! )

Good Luck!