Volkswagen Golf Workshop Service and Auto Repair Manuals

→ In order to reduce the amount of pollutants in the exhaust gas, air is fed in behind the exhaust valves. The suction of the exhaust gas draws air from the air cleaner and it passes through the silencer -1- and the check valves -2- into the cylinder head.

On Scirocco vehicles with manual gearbox, a cut-off valve stops the flow of air during overrun.

Testing check valves

Damaged check valves have a detrimental effect on the exhaust gas composition. When they are defective, the valves turn blue on account of the heat and the attached rubber hoses are destroyed. In such cases the check valves and hoses must be renewed.

Checking cut-off valve

• ‒ → Pull off hose between air cleaner and cut-off valve -arrow-.
• ‒ Run engine at idle.
  The valve must be open (cone downwards).
• ‒ Briefly increase engine speed to approx. 4500 rpm by opening throttle and abruptly close throttle. Valve must close (cone upwards).