Today, Brake Vacuum Pumps are seen fitted on the cylinder head and driven by the cam Shaft, the aspirated air is generally conveyed into the the cylinder head.
Such Vacuum pump is constructed with either rotating elliptical vane or oscillating plunger on cam disc (diagram below) which is considered one of the latest technology ( This technology is first widely used on Diesel Engine in the early days)
However we have seen a transient life span of these high stress pumps. They require lubricating oil for Cooling as well as sealing. Oil is generally supplied by ducts in the cylinder head or the Cam Shaft , the oil is vent back into the engine along with the exhaust air. Maintaining fresh oil and optimal oil level will definitely prolong the product reliability