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TT · Reliability

TT Diverter valve

Your TT

Pick your year to see what fits.

There was no 2007 TT in the US. The 225, 3.2, TTS and TT RS are always quattro.

Holds boost
Easy$245–$27030 min
All TT mods

Why do it

The stock plastic diverter valve tears and leaks boost, which makes the car feel flat. A metal replacement holds boost and lasts.

Tools you'll need

Parts to buy

Double-check fitment before buying.

Before you start

  • The Forge valve comes with a few springs. Stock cars keep the spring that's already fitted; tuned cars usually need a stiffer one (the chart in the box says which).
  • Have a small hose clamp handy in case an old clamp breaks.
  • The valve is on the back of the engine, on the turbo, reached from under the car above the passenger-side axle. The video is on a VW GTI with the same 2.0T valve.

Video guide

Forge diverter valve install on a TT Mk1
by Car Chris on YouTube

The exact Forge valve we list, on a 1.8T TT.

Watch the whole video

Steps

  1. Fit the right spring

    • If you need a different spring, remove the three Allen screws on top of the valve, swap the spring and tighten the screws back down.
    Watch this step (2:07–2:53)

  2. Remove the engine cover

    • Undo the two cover fasteners and lift the cover off. The diverter valve sits on the hoses near the front of the engine.
    Watch this step (2:53–3:09)

  3. Remove the old valve

    • Loosen the hose clamps on the lower and upper hoses, unclip the small vacuum line on top, and pull the old valve out.
    Watch this step (3:09–3:41)

  4. Fit the new valve

    • Put the new valve where the old one was, tighten both hose clamps firmly, and refit the top vacuum line with the cable tie from the box.
    • Refit the engine cover.
    Watch this step (3:41–4:11)

  5. Test drive

    • Drive normally and listen for a smooth whoosh between gears. A hissing sound means a loose clamp.
    Watch this step (4:11–5:27)

  6. Find the valve

    • Raise the front, remove the passenger-side wheel, and look up behind the engine above the axle. The valve bolts to the turbo with an electrical plug on the bottom.
    Watch this step (Deutsche Auto Parts) (2:47–3:17)

  7. Remove the old valve

    • Unplug the connector, then remove the three 5mm Allen bolts with long extensions. The valve comes straight out.
    Watch this step (3:17–4:06)

  8. Fit the new valve the right way round

    • A small nub on the valve lines up with a hole on the turbo, so it only sits flat one way, with the plug facing down.
    Watch this step (1:56–2:32)

  9. Tighten and plug in

    • Snug the three bolts (no need to go crazy), plug the connector back in, and refit the wheel.
    Watch this step (4:06–4:48)

How to know it worked

Did this guide work for you?

Safety first

  • Park on flat ground, set the parking brake and chock the wheels.
  • Never get under a car held up only by a jack. Use jack stands.
  • Let the engine and exhaust cool first.
  • Disconnect the battery before unplugging electrical parts.
  • Wear safety glasses.
  • If something doesn't match your car, stop and ask a shop.

Follow your part's instructions and your service manual's torque specs.