The 1.8T is a turbocharged, four-cylinder engine that has been used in a variety of VWs and Audis. This engine is powerful and reliable. The 1.8T uses a diverter valve (also known as a pressure relief valve) mounted on the manifold that is designed to release air pressure in the intake when the throttle is lifted or not in use. The 1.8T can suffer from a leaking diverter valve, which reduces turbo boost pressure and power. You can replace the old valve with a new one in a few steps.
Open the hood. Remove the plastic engine cover by turning the fasteners 90 degrees so they pop up. Pull the cover off the engine and set it aside. On new VW Beetles, the cover is removed by first removing two trim caps over two 10-mm bolts. Remove the bolts with a socket, then slide the cover forward and up.
Remove the turbo boost hose from the diverter valve. These will be held on by hose clamps, the style of which depends on the model. On some you simply squeeze the clamps with the pliers and slide them off the hose. Other models use a crimp clamp that needs to be pried open with the screwdriver. You can also cut the clamp with tin snips.
Remove the vacuum hose that fastens to the top of the diverter valve. Grab the hose with your hands and pull it off by wiggling it back and forth.
Loosen the clamp at the bottom of the valve with the flat-head screwdriver. If it uses a crimp clamp, removeit in the same manner as Step 2. Remove the diverter valve.
Install the new diverter valve. Tighten the clamp at the base with the screwdriver. If the clamp was a crimp-style, replace it with a conventional screw clamp.
Reinstall the vacuum line on the top of the diverter valve by sliding it on, ensuring that it is firmly seated. Reinstall the boost hose. Reuse the old clamp or install a new screw clamp if it used a crimp clamp. Reinstall the engine cover.
