The diverter valve is a component of your Passat’s turbocharger, and its job is to divert and release boost when the throttle is closed. Without the diverter valve, pressure can bounce off the closed throttle plate back to the turbo’s compressor wheel, stall it, and potentially damage the turbo.
While driving, you’ve inevitably noticed a “psh” sound come from under the hood of your Passat—this is the sound emitted by the diverter valve when it’s working correctly. OEM diverter valves are made of plastic and utilize rubber diaphragms inside that are susceptible to tearing with age.
Once this rubber diaphragm tears you will receive a boost leak right at the turbo. A boost least can cause:
- A noticeable loss in performance (if your Passat is equipped with a boost gauge it will show a drop in boost levels while under acceleration)
- Excessive noise or air surging while under acceleration
- Fault code P0299: turbocharger under boost
If you’re experiencing any of these symptoms, here’s a step-by-step explanation on how to go about the very simple process of replacing your failing diverter valve.
- Vehicle jack and jack stands
- 5mm hex key or hex socket with extension
Step One: Preparing Your Passat
- Apply the parking brake and chock the rear wheels.
- Lift the vehicle with the jack utilizing the double pinch welds located underneath the lower rocker panels (i.e. the areas under your doors).
- Once the vehicle is at an appropriate height, secure the car with jack stands and ensure it’s sturdy.
Step Two: Locate Your Diverter Valve
- Maneuver under the passenger side and locate the soon-to-be old diverter valve. It’s attached to the turbo located on the backside of the engine, right above the axel. It is a small black square with one wire plugged into it, held in place by three hex bolts.
Step Three: Remove Your Diverter Valve
- Unplug the wire from the diverter valve. It has a single release, so simply use your thumb to release the clip and slide the connector off.
- Locate the three hex bolts holding the diverter valve in place, and remove them using your 5mm hex key.
- Once it’s broken loose, remove the diverter valve and inspect the orange or teal colored rubber diaphragm for damage.
Step Four: Installing Your New Diverter Valve
- Secure your new diverter valve in place with the same three hex bolts, and reconnect the wire.
- Make sure the bolts are tightened securely and the new diverter valve is properly seated up against the turbocharger. If the diverter valve is not sealed properly there’s a possibility of another boost leak or an oil leak.
Step Five: Wrap Up
- Lower your Passat off of the jack stands and remove the chocks from the rear wheels. The fault code/check engine light should go away on its own once your Passat learns the issue has been addressed. If for some reason it doesn’t, just take it to a local auto parts store that provides free scanning service and they can clear the code for you.
Congratulations, you’ve successfully replaced your diverter valve! Simple enough, right? Now you can enjoy the restored performance of your Passat!
Make sure to document the repair and your Passat’s mileage for your records. If this occurs again, consider purchasing a “revision D” version diverter valve, which utilizes a piston style valve instead of a rubber diaphragm.