Function Vacuum Control

Identification Of Vacuum Lines

The basic color of the vacuum lines for the automatic transmission is black. The lines are identified for the different functions by means of color stripes.

Abbreviated designations in vacuum flow charts:

br = brown
gn = green
rt = red
sw = black
ws = white

Vacuum Flow Chart





The vacuum control for modulating pressure differs compared with engine 617.95 in its pneumatic activation.

Function
With the engine running, the centric connection (VAC) of vacuum transducer is connected to full vacuum, connection (VCV) is connected to controlled vacuum.

Coolant temperature < 50°C

The switchover valve (Y 29) is connected to ground via temperature switch (S25/6) for connection 2-3. The vacuum controlled by the vacuum control valve rests against connections (PRE and VCV) and acts directly against the vacuum at connection (VAC). This will result in the vacuum at connection (TRA) required for transmission control.

Coolant temperature > 50°C

The ground connection on switchover valve (Y 29) is interrupted, the valve switches 1-3. The connection (PRE) is now connected with the boost pressure line of the exhaust gas turbocharger. When the boost pressure is starting, it will act against the vacuum controlled by the vacuum control valve. This will result in a reduction of the vacuum at connection (TRA) and the modulating pressure will therefore be increased via vacuum capsule on automatic transmission.