Thank you Savannah, I will probably invest in a mechanics stethoscope.

 

On thing owners should keep in mind when listening is bending too close and long hair (boys and those foxy gals, and those suave island guys with dreadlocks) getting snatched by a pulley, etc. Safety glasses are also a good touch, because the belt can catch and throw things back at you.

 

For the interest of others who may have a similar issue it turned out to be my alternator bearings. The stethoscope helped greatly. Thank you again Savannah.

 

Those MM alternators are high dollar and can be rebuilt. Did you keep it or use it for a core charge?

When I got a used one, the core chg was only ten bucks, so I kept my old one for rebuilding.

 

Core charge, it actually looked pretty new when I bought my truck a few months ago. I have a massive battery drain going on now. I think that's what killed it. My Disco dies immediately after I disconnect the jumper cables, I bought a new battery the same day.

Stupid question, what's MM? Was that a good alternator I had?

 

MM is Magnetti Marrelli (brand name) made in Italy and very robust/waterproof.
They can be rebuilt with new brushes (considered a normal wear item). Also new regulator subassy, and bearings and such.

A lot of the replacements available from chain auto parts stores are rebuilt in off-shore locations with the cheapest components available and are considered by most to be rather inferior to the original MM brand.

Yours may have been one of the cheap rebuilt ones. I have my origial MM I just swapped out with a used one I bought from a recycler that is a rebuild. My tach had quit working and the MM was beginning to get a little noisy. The replacement I bought used was $40 plus a $10 core charge. I kept the MM to rebuild.

 

I wish I would have known, I'd have kept to try a rebuild.

 

If you scout around, you may be able to find one at a junkyard or similar place now that you know. It has a very distinctive label on it and says made in Italy.