1986 Alternator replacement- Rumbling noise now gone, hidden bolt on A/C plate

[Missed Approach]

Background: 1986 3.2 Coupe, now with 140K.

The issue: A low rumbling growl that could also be felt when I placed my hand on the fiberglass shroud cover. I first noticed it two years ago, and it has been getting progressively louder. (It was getting especially loud at idle.)
It was the exact same sound as 911 Euro posted: 1984 Porsche 911 Euro Engine Noise on his YouTube link. https://www.youtube.com/watch?v=7O5r2Cu5yQc&feature=youtu.be

Checked her records, and the alternator was last changed in 1996. All indications (I hoped) pointed to alternator bearings going bad. Plus, I really wanted to clean up the Magnesium fan and housing.

I had the damnedest time trying to loosen the A/C compressor plate to remove the belt. As it turns out, I really need to read the manual better. There are four (M8 Hex) Bolts holding down the plate. The one on the upper right side is absolutely buried- you have to find it by touch!



The alternator replacement process (using a rebuilt Bosch unit) was relatively straightforward. I used all new hardware from our host, and I used 4 outside, 2 inside for Pulley Shim placement.



The Result: Noise is gone, new (Porsche-branded) belts and a clean fan and shroud. As an aside, I used Purple Power and a Scotch-Brite pad on the Mg- seemed to work well.

[911obgyn]

If you spray the magnesium with Boshield or Gibbs the finish will last longer

[Missed Approach]

Thanks @911obgyn! That was a concern- there appears to be a West Marine near me that has Boeshield in stock!