Alternator tensioner bolt

[Steve]

Any ideas on what would be causing my tensioner bolt to loosen out repeatedly all of a sudden?
Have reset it each time but within a couple of days its back out again and would have lost if completely had the belt not started making noises.
Would rather fix than bandaid it with threadlock.

Thanks

[DIL2307]

Try a different (new) alternator pivot bolt, this kept happening my mx5 when I got it first, it would work itself loose or wreck the belt in as little as 50 miles. I couldn't see anything particularly wrong with the bolt but when I replaced it the problem went away

[sidewaysreilly]

Bolt has stretched part its elastic limit and will shear unless replaced . Use a 10.9 grade one

[Steve]

Thanks for the replies, I'll order both bolts.
Cheers,
Steve