Heavily oiled alternator with vacuum pump
In some vehicles with diesel engines, the required vacuum for the brake booster is generated by a vacuum pump attached to the alternator. A common problem is for these alternators to get completely oiled, causing them to fail.
One of the most common causes of this problem is the seal between the alternator and the vacuum pump. This seal, usually achieved with a rubber ring, becomes leaky due to ageing but also after replacing the alternator. Often the rubber ring is not renewed and the alternator fails after a short time because of oil seeping in.
Oil penetration can damage the alternator within a very short time and lead to failure.
The seal between the alternator and the vacuum pump should always be renewed when the components have been separated. Also check the oil and vacuum hoses on the vacuum pump for leak tightness.