What It Is
A billet fitting that eliminates the plastic thermostatic tee on the fuel filter, giving you a cleaner, more orderly engine bay in the process. It includes a tube for the hose ends coming off the thermostatic valve, so everything routes neatly once installed.
Why Bypass the Thermostatic Tee
The factory plastic tee is meant to close off at 85°F, but it isn't fully trusted to do so reliably. Bypassing it prevents hot fuel from the injection pump return recirculating back into the pump's suction side. It also removes a common source of "bubble trouble" in fuel lines, caused by a failing seal on the plastic tee.
Fitment
2002-2006 Mk4 Golf, Jetta, Jetta Wagon, and New Beetle, and 2004-2005 Passat.
Common Questions
Why would I want to remove the thermostatic tee?
It's meant to close at 85°F, but the seal isn't fully reliable, and a failing seal is a known cause of air bubbles in the fuel line. Bypassing it also stops hot return fuel from recirculating back into the injection pump's suction side.
Is this a functional part or just cosmetic?
Both. It solves the recirculation and sealing issues of the factory tee while also cleaning up the look of that part of the engine bay.
What's it made of?
Billet, with an integrated tube for routing the hose ends that were previously connected to the thermostatic valve.
