Alternator FULL of OIL!!! What went wrong?

Dealing with all subsystems specific to the diesel powered Datsun-Nissan 720 pickup trucks.

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Alternator FULL of OIL!!! What went wrong?


Post by justanother54321 »

'82 SD22. My alternator went out the other day. Pulled it off and it is full of motor oil.

There are no signs of oil leaks outside vacuum pump.

I pulled the vacuum pump, and it looks like it came into the alternator via the alternator spindle shaft.

Where is the seal that keeps oil out of the alternator? Inside the alt. behind the spindle shaft or inside the vacuum pump?

I have a rebuilt alternator on hand but I don't want to throw that in if the vacuum pump is the culprit.

Also, any microfiche on the vacuum pump?

Any help is much appreciated.
1982 720 SD22 CA Emission
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Location: Middleburg, Fla., U.S. of A.


Post by Cmdr.Ron »

Did you find both o-rings?
FSM page BR-15 has an exploded view of the vacuum pump (almost better than it looked in pieces).
That's the Brake section. It's only there to pull vacuum for the brake booster.

Smaller o-ring on outside of cover plate; larger one on the inside.

That puppy gets major oil supply to keep it well lubed.
The first time I put mine back, I missed re-timing the rotor vanes. (FSM doesn't show that.) It rotated 1/2 a turn & locked. The starter couldn't overcome it, fortunately.
'82 Datsun 720 SD22, '81 Toyota HiLux (proj)'77 Fiat 124 Spider trike project.
The Blessing of Abraham is mine.
jim bob
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Re: Alternator FULL of OIL!!! What went wrong?


Post by jim bob »

I could have solved a lot of problems if I had known about this site sooner. To answer your question the seal is in the alternator. Failure of this seal can empty your crankcase. Also before you replace the seal, check the shaft for wear, as this may cause premature seal failure.

Anybody that has questions about mid 80s Nissan p/u s email me, I may be able to hip I check my emails more regularly than any forums, which I may, or may not know about, as I'm slowly finding my way around the internet.
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