1982 240DL B21F-MPG

Don't know what happened, but it left it loose at one time, maybe ended up with damaged bolt threads. I tightened it a month or so ago, and noticed yesterday that the alternator belts were loose. Took things apart and had that sinking sensation as half a bolt was attached to the upper alternator slider (the one that goes through the bushing into the block).

If you've ever seen Monty Python and the Holy Grail, where the king is explaining how he "Built a castle, and it sank into the swap. So I built another castle and it sank into the swamp too. Then I built a third castle, it burned up, fell down, then sank into the swamp..."

I tried the left hand drill bit hoping that the bolt would spin out as I drilled it. No luck. Then I tried a tap like thread extractor (*because easy-outs break off all the time*). Know what? They break off too. Center punched the remains of the thread extractor a few times, started drilling into it, realized too late I was off center and mangling the block threads. My last heroic attempt was the helicoil route. I drilled a 21/64" hole into the block, no problems. Next the helicoil tap went in. Just as it was starting to thread in nicely, it bound up somewhat. I backed off, went forward again for another bite, applied a little more pressure and IT BROKE TOO!!! Disaster!

There's a good piece of the tap threads hanging out, but I think I'm going to pay the pros to clean up the mess I've made.

Here's a question for you all: On the block, right above the alternator bolt hole, theres a threaded plug going into the block, with a square keyed opening. Anybody know what it's for? Someone say it's the emergency backup alternator mounting hole!

Greg