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Turbocharger - exploded view > < Effects of leaks

A4 Mk2

Checking mechanical air recirculation valve
Checking mechanical air recirculation valve
  Note
t  The mechanical air recirculation valve is located upstream of the turbocharger. It is opened by vacuum from the air recirculation valve for turbocharger -N249- when the engine is on overrun or under part load or when idling. This dissipates the charge pressure upstream of the throttle valve and maintains a higher turbocharger speed.
t  Check air recirculation valve in the event of loss of power or load change jolts.
Special tools and workshop equipment required
   
t  Hand vacuum pump -V.A.G 1390-
  W00-0515
Test sequence
–  Connect hand vacuum pump -V.A.G 1390- to air recirculation valve.
–  Operate hand vacuum pump.
l  Air recirculation valve should open -arrow-
–  Operate air vent valve on vacuum pump after about 30 seconds.
l  Air recirculation valve should close -arrow-.
If air recirculation valve does not open/close or if valve plate does not provide a tight closure when air recirculation valve is closed:
–  Renew air recirculation valve and secure hose connections with hose clips.
  V21-0074

Turbocharger - exploded view > < Effects of leaks