Nice.

The return hose from radiator flows at all time engine is running and is where air is released from the system to atmosphere. That’s why there is a bleed screw to assist in first bleeding air after changing coolant as well as one on the head.

If smelling coolant don’t rule out leaking heater matrix also. Not sure if coolant would end up on the carpet or drain out underside.

Sounds like a win on the cap.