Reduced brake power assistance after prolonged manoeuvring

E39, E38 / M57 Complaint:Reduced brake power assistance after prolonged 
manoeuvring without throttle actuation (”hard brake pedal”).
Cause:Unfavorable tolerance zones between vacuum pump feed capacity and 
brake booster servo vacuum requirement when the engine is idling lead to 
reduced brake power assistance after repeated brake applications.
Affected
vehicles:E38/E39 with M57
Manufacturing period:
Automatic vehicles: start of series production until July 2000
Manual vehicles: start of series production until January 2001
Remedy:In case of customer complaint, retrofit a larger vacuum pump with 
greater feed capacity.
Procedure:Remove vacuum pump, please refer to Repair Instructions for 
E38/E39 11 66 000.

A fastening lug must be installed in order to fit the new vacuum pump. This 
allows the existing screw connections to be used. A new moulded hose allows 
the vacuum line to be secured to the vacuum pump.

The fastening lug is fixed at the top to the ”old” vacuum pump screw 
connection and at the bottom to the EGR cooler anchorage on the cylinder 
head.

The acoustic cover must be replaced with a version modified to fit the shape 
of the new vacuum pump.