E60 Coolant sensor Dimensions of sealing ring and sealing return hose on the cooler

Hello together On my son’s 5s either the seal ring of the coolant sensor or the seal of the return hose is minimal leaking. Could I not locate exactly yet. Does anyone know the size of the seal ring of the sensor? I don’t see how to change the complete sensor for a 5ct O-ring. On the old Z4 it was 10×3. Maybe it’s the same with the E60. How are the return hoses fixed to the cooler? Are they only plugged on and there possibly also an O-ring?