For a long time its work in vehicles was done without control through the throttle flap. This applies not necessarily only to the
Diesel engine. Nowadays, there are also petrol engines
without throttle flap control. The pneumatic brake booster has by far, the most frequent need for vacuum. It used
to be, e.g., the door-locking, the pop-up headlights and the selector requirements for the all-wheel drive or the limited slip differential.
The vacuum pump, in modern Diesel engines, is also found there, where in the petrol driven engine previously, the distributor was mounted. The above shown cut-open model is mounted at the end of the camshaft.
The brake booster is then fitted to the long connection on the right. From there (filtered) air is sucked in and pumped into the engine. Slightly to the right, the two claws and the drive shaft for the pump can be seen. In the
center of the shaft, sealed by an O-ring, is an oil bore, through which oil is mixed into the sucked in air. It provides the lubrication for the crosspiece, which is constantly moving in the shaft-end. The friction of the sliding
blocks at the end of the crosspiece also need to be lubricated. They seal the two areas which change with the rotation. The air outlet is found exactly below the shaft. On its way through the engine, the air is again freed
from the oil and supplied, somewhat cleaned, to the intake air. 12/10