The Volkwagen Auto Group (VAG) designed the Passat as a midsize sedan platform in Europe, though it qualifies as a small car in the North American market. The Passat platform is also used by Audi for their A4 sedan and station wagon. Some Passat cars are offered with turbocharged engines that boost the air pressure in the combustion chambers, leading to more power. However turbochargers need blowoff valves to prevent that overpressure from blowing back into the turbocharger and damaging the turbine blades. If the valve malfunctions, then it needs to be replaced immediately or the overpressure can damage the turbocharger and engine.
Park the Passat in your driveway and pull the emergency brake up. Pull the hood release latch, then turn the Passat off. Prop the hood up and disconnect the black cable from the car battery to protect yourself from electrical shorts. Put drop cloths on the edges of the engine bay to protect the paint.
Locate the turbocharger downpipe; the Passat's blow off valve is attached to the side of the pipe. Pull the vacuum line top from the top of the blow off valve by hand. Unscrew the O-ring clamp that secures the bottom of the valve to the downpipe port. Pull the old blow off valve off and place it to the side.
Plug the new blow off valve into the port on the downpipe. Screw the O-ring clamp onto the bottom of the blow off valve until it is tight and will not budge. Plug the vacuum line in on the top of the blow off valve. Reconnect the black wire to the car battery and shut the Passat's hood.
Turn the Passat on and take it for a test drive. If the Passat blow off valve is installed correctly, the engine speed will drop suddenly once you exit the turbo power band. If the engine speed stays elevated after fast driving, then the blow off valve is not working right. The vacuum line may have come off or the blow off valve spring may be broken.
