The lower alternator bolt - the long bolt that runs through the pivot - has come off of several of my 240s over the years. Cars vary by year, miles, condition.

Usually the nut falls off and allows the bolt to come forward until it's free of the pivot; whereupon the alternator is pulled up and away y the belts. It makes some noise and usually lets me get home.

This happened yesterday on my 91. I'd checked it ~ 1,000 miles ago at the last oil change and it was tight.

Has anyone else had this problem repeatedly?

I think that the bolt is just not long enough for the lock nut to seat properly ie. the locking part of the nut isn't catching wenough threads. I use two large washers on mine - perhaps it should have one or none.

I'm thinking of getting a slightly longer 5/16" bolt and securing it with a double nut.

I've had to fix this a couple of times on the road. Usually the bolt just vibrates back into position after the alternator lifts out but sometimes it falls out. I've rigged it from below with wire and a bungee cord to get home.

This kind of repair is why I don't use the lower shield.
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240s: 2 drivers and some parts cars