u/_Vanderbosch

Hello everyone!

Back Story: I have a 1991 Mitsubishi Delica L300 that started to have some alternator squeal. There are two belts on the alternator and when checking the tension, one of them was slightly looser than the other. Based on research on the delicaforums, the alternator pivot mount (made of aluminum) can oval out over time due to vibration going through the steel mounting bolt. This causes the alternator to sit at a slight angle which causes belt tension issues.

There are two ways to fix this:

1. Replace the bracket. Unfortunately this is a pretty big job.
2. Drill the mounting hole from the original 8mm to 10mm. You can either sleeve it back to 8mm or use a later model alternator that uses a 10mm bolt. The location of this mount makes drilling this straight a little sketchy but it looks like it might be possible with a right angle drill.

What is the best way to drill a slightly ovaled 8mm hole to 10mm through 2-3/16" of aluminum keeping in mind the very limited access?

Thanks again for any info!

Ovaled Hole

Pivot Mount in its Entirety

View from above and below of the pivot mount (tight space)

slop in the pivot mount