2004 Volkswagen Passat GL 4 Cyl 1.80L
How to find coolant leak near water pump?
Leaking coolant top rear of motor
If you can't see the leak, you'll have to take it to a repair shop. The repair shop will pressurize the cooling system (with the engine cold) to locate the leak. It could be a hose connection or a water pump gasket or seal.