While replacing the engine cooling fan in a VW Passat is relatively simple compared to other VW vehicles, be warned that a different procedure applies to each engine configuration. These steps apply to the 2.8L VW Passat engine. A novice can accomplish this task in about an hour and you will need a few special tools for the job.
Disconnect and isolate the negative battery cable using a normal wrench or screwdriver. Never skip this step when working in the engine compartment of your VW Passat.
Use pin wrench #3212 or an equivalent to hold the viscous fan coupling pulley in place, and then remove the coupling with open end wrench #3312 or an equivalent. It's very important that you note this coupling has a left-hand thread; it must be rotated opposite the typical direction to loosen and remove it.
Lift the viscous fan coupling upward out of the vehicle. Replace the fan unit and tighten the coupling to 30 foot pounds (40 Nm) of torque. Remember that this is a left-handed thread and must be tightened opposite the usual direction. This tightening torque only applies when used in conjunction with pin wrench #3212; don't substitute another tool.
Reconnect the negative battery cable and run your vehicle up to normal operating temperature. Check for normal fan operation.
You don't have to drain the coolant to replace the cooling fan on a VW Passat.