Volkswagen Workshop Service and Repair Manuals

In order to keep he amount of poisonous nitrous oxides (NOx) to a minimum, exhaust gas is recirculated into the combustion air in the part load range when the engine is warm.

→ At coolant temperatures above 49 °C the thermopneumatic valve opens and allows vacuum from the intake manifold to become effective at the EGR valve. A diaphragm in the EGR valve is actuated so that exhaust gas from the exhaust pipe is routed throught the exhaust gas filter back into the intake manifold.

Checking EGR valve

• ◆ Minimum engine oil temperature 60 °C

• ‒ Allow engine to idle.
• ‒ Pull vacuum hose off EGR valve.
• ‒ Pull vacuum hose off anti-backfire valve and connect it to the EGR vavle. The engine idle should then become uneven and the pipe on the EGR valve should get warm.

Checking thermopneumatic valve

• ‒ → Remove thermopneumatic vavle and heat/cool in water bath.
• ‒ Blow throught valve.

• At temperatures
• ‒ below + 27 °C it must be closed
• ‒ above + 49 °C it must be open