How to repair flood of coolant on passenger side back seat floor as the Coolant Expansion Tank being filled with coolant in 2000 Volvo s70

What is your question?

Coolant seems to flow right through to Passenger back seat floor when trying to fill the Coolant Expansion Tank with Coolant in 2000 Volvo S70 Sedan .

How long has your 2000 Volvo S70 had this problem?

ABOUT A MONTH .