Applicable Vehicles :
- Volkswagon Golf GTI 2008-2012
How to tell if you have a problem :
While an all around great performing car there were occasional issues with the factory diverter valve from VW. This problem is pretty readily identifiable by a whistling sound coming from under the hood typically around 4000rpm, though it can present itself in other parts of the rpm range as well. This can often times cause a sudden loss in boost pressure. Make sure the whistling is coming from the valve itself and not a poorly tensioned or failing belt.
How to Fix Problem:
Typically replacing the unit with a "Revision D" diverter valve from VW can fix the problem. Otherwise going with an aftermarket bypass valve can also rectify the issue.
- Diverter Valve
- Diverts excess intake tract pressure after closing the throttle performing similarly in function to a bypass valve or blow-off valve.