Volkswagen PASSAT Repair Manual page 196

Assembly overview - hydraulic unit, brake servo/brake master cylinder
http://ebahn.bentleypublishers.com/vw/servlet/Display?action=Goto&type=repair&id=VW.B4.SU01.45.4
Installing
Note:
When installing new circlip ensure opening is
uppermost - installation position (arrow).
- Install new sealing ring to sensor. (Coat sealing
ring with lubricant e.g. soft soap).
- Sensor notch must point downward when inserting
into brake servo and be heard to engage.
- Connect sensor unit connection and ensure
correctly located.
Note:
To ensure correctly seated pull senor by hand.
Leaks at the sensor sealing ring, result in
insufficient braking vacuum and poor engine
idling.
For ease of illustration, shows installing the
sensor with brake fluid reservoir removed.
Page 10 of 10
45-27
12/7/2004