We are now on to our third brake vacuum pump on a car with this engine and they are failing quickly, which may suggest that the oil is not feeding to the vacuum pump. I understand, however, that it is impossible go investigate this properly without removing the left cylinder head to check the oil feed. Has anyone encountered such a problem with this engine in any of the 320 CDI cars? Could it be caused by carbon build up even although there are no other symptoms whatsoever of such a problem? The other thing that puzzles me is that if the brake vacuum pump could be failing due to lack of lubrication and become stiff, would this not cause some kind of problem for the engine as it is cam driven? Any experience appreciated.