Diesel engines do not produce manifold vacuum, vacuum is requited to operate the brake booster, so on diesels a separate vacuum pump is used. Many Asian engines use a pump that is attached to the back of the alternator to supply vacuum to an accumulate (a vacuum storage tank) the oil supply is solely used to lubricate the vacuum pump. There will be a pressure hose from the main oil gallery and a drain back hose to the sump, a seal in the back of the pump keeps oil out of the alternator.
User notes: The seal is located inside the alternator that prevents oil from getting inside the alt. The o-ring between the vacuum pump and alt only stops oil from leaking between the two parts.
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Monday, November 19th, 2012 AT 9:17 AM