Has anyone looked closely at the rear of a bosch alternator from the outside or replaced the bearing. There is a small hole there. I can understand why this would be there. For lubricant, or to let water in to ruin the bearing when washing the engine like on my alternator. See the pic

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Hmmmm I'd think it's there to prevent air lock when putting the casing in place. likely there is a steel cup on the other side that holds the actual bearing.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
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This is a pic of the Alternator that would go on mine. There is a lot of holes/places for Water to get into the Alternator. So the small hole seems like the least problematic of the ways Water can get in.

As V said. The Hole is there to allow Air to get out when the Bearing goes in. Instead of the Needle Bearing as on the Old US Alternators the Bosch actually uses a shielded Ball Bearing.

If the little hole was not there the Bearing is pressed into the Housing followed by the Shaft being pressed in or if the Bearing is already on the Shaft ant the whole thing pressed in it would trap Air in there and the Air would try to go through the Bearing a push Lubricant out of the Bearing.

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84 300D, 82 Volvo 244Gl Diesel

Absolutly! to both Diesel 911 & vstech. How dumb of me and observant of you. That totally makes sense to me now.
I think now that the bearing has been replaced I will plug up the hole. I don't like water getting in back there and sitting. From taking a close look at the bearing I took out it seemed to have pitting on the bearings thought there was still grease in there.

What I find odd is that on the Mercedes and My Volvo Diesel the Alternator is about in the same position. I don't understand why they would mount an Alternator so low that if you needed to ford a flooded area the Alternator is going to get Water in it?

The Volvo has a single Belt and when it gets wet is squeels till it is dry. It may be the chance of the Belts gettitn wet is the reason Mercedes uses 2 Belts.

Usually on the older US made Cars the Alternator is higher up.

But, all of the Alternators need the holes so that the Fan on them will circulate cooling Air through them

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84 300D, 82 Volvo 244Gl Diesel

They should be sealed bearings.

The operating temperature quickly boils off any water.

.

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