Volkswagen Workshop Service and Repair Manuals

In order to keep the 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.

Vehicles with manual gearbox

Above approx. + 68°C the exhaust gas is recirculated continuously except at idling speed and full throttle. Below approx. + 52°C a thermopneumatic valve interrupts the vacuum flow and closes the EGR valve.

Checking EGR valve

• ◆ Minimum engine oil temperature 60°C

• ‒ Allow engine to idle.

• ‒ → Pull vacuum hose off retard unit on distriburor (engine speed increases).
• ‒ Pull vacuum hose off EGR valve -arrow- and attach hose of retard unit.
  The idle speed must then drop noticably and the pipe on the EGR valve should get warm.

Checking thermopneumatic valve

• ‒ → Remove themopneumatic valve and heat it or cool it in a water bath.
• ‒ Blow through valve.

• At temperatures
• ‒ below approx. + 53 °C it must be closed
• ‒ above approx. + 68 °C it must be open

Vehicles with automatic gearbox

At coolant temperatures in excess of 49 °C thermopneumatic valve opens and - under part load conditions - routes exhaust gas out of the exhaust manifold into the intake manifold via a pipe and the EGR valve.

Checking EGR valve

• ◆ Minimum engine oil temperature 60 °C

• ‒ Allow engine to idle.
• ‒ Pull vacuum hose off EGR valve.
• ‒ Pull vacuum hose off throttle for pulldown unit and connect to EGR valve.
  The engine idling should then become uneven and the pipe on the EGR valve should become warm; otherwise the valve is to be renewed.

Checking thermopneumatic valve

• ‒ → Remove thermopneumatic valve and heat it or cool it in a water bath.
• ‒ Blow through valve.

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