Alternator Disassembly
Thread Starter
Le Mans Master
Joined: Oct 2000
Posts: 8,897
Likes: 1,357
From: Santa Ana CA
Alternator Disassembly
I want to use the mount hole on the back of my alternator (internally regulated Delcotron) and of course the threads are stripped out so I need to install a helicoil. 
Can I simply remove the four bolts and pry the case apart to drill out the old threads in the back and install the helicoil, or is this even necessary? Certainly there is room to do this in the car without even unmounting it.
I'd hate to hit the rotor drilling out the old threads or get a bunch of aluminum shavings in the case. On the other hand, I'd hate to take it apart if I couldn't get it back together and working again or if it means scratching the polished aluminum when prying the back off. :o
Thanks
Can I simply remove the four bolts and pry the case apart to drill out the old threads in the back and install the helicoil, or is this even necessary? Certainly there is room to do this in the car without even unmounting it.
I'd hate to hit the rotor drilling out the old threads or get a bunch of aluminum shavings in the case. On the other hand, I'd hate to take it apart if I couldn't get it back together and working again or if it means scratching the polished aluminum when prying the back off. :o
Thanks
Melting Slicks
Joined: Dec 2009
Posts: 3,235
Likes: 658
From: Thunder Bay
Its been a few years since I've had one of these apart, but I have rebuilt many of them. They come apart pretty easy as I recall. If you just have to get the back half of the case off, you just take out the bolts and pull. I think the brushes are in the front, so if you leave the front half assembled, you can just remove the back half of the case. If I'm wrong and the brushes are in the back, you just hold them in place with a couple of paper clips to reassemble and pull the clips out when you're done. If you're enough of a mechanic to know how to install a heli-coil, you shouldn't have any problem with an alternator. Good luck.
Le Mans Master
Joined: Aug 2006
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From: mount holly NC
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Team Owner
Joined: Jan 2006
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From: Crossville TN
You should definitely disassemble the alternator to do any helicoil and/or tapping operation. Loose metal chips in an alternator is a No-No 
. If you are talking about a stripped thread in the mounting 'boss' on the back of the case, you should have no trouble repairing it. I don't remember, but if that is a 'blind' threaded hole [not open at the bottom] you will need a bottoming drill and tap to put threads in for a helicoil.
. If you are talking about a stripped thread in the mounting 'boss' on the back of the case, you should have no trouble repairing it. I don't remember, but if that is a 'blind' threaded hole [not open at the bottom] you will need a bottoming drill and tap to put threads in for a helicoil.
Safety Car
Joined: Jun 2004
Posts: 4,380
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From: Beecher Illinois
Pretty much everything is in the back half of the alternator. When you pry it apart make sure that steel middle section(stator?) goes with the back half.
Like mentioned, the brushes will pop out. Just work them back in place and insert paper clips from the outside through the holes provided to hold em back in place for reassembly.
Pay attention to how everything is mounted if you continue disassembling and lay it out on the bench in order as you take it apart.
Like mentioned, the brushes will pop out. Just work them back in place and insert paper clips from the outside through the holes provided to hold em back in place for reassembly.
Pay attention to how everything is mounted if you continue disassembling and lay it out on the bench in order as you take it apart.
Thread Starter
Le Mans Master
Joined: Oct 2000
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From: Santa Ana CA
Excellent. Thanks guys.
This is one of those "polished" 100-amp alternators and the 5/16" theads in the upper mount are also shot. I have to use a nut on the tensioning bolt instead of just bolting the alternator directly to the J-bar, but have just lived with it. You would think that when they go to the trouble to rebuild an alternator, change out the gut, and polish it, they would put helicoils in the threaded holes instead of leaving them stripped out.
When I was checking out the old threads, I ran a Q-tip in the hole with vasaline on it and a few circular "thread" pieces came out stuck on the Q-tip. I actually had an 8MM bolt (just slightly bigger than a 5/16") in it just to hold a ground wire, but now this bolt is going to see some serious action.
This is one of those "polished" 100-amp alternators and the 5/16" theads in the upper mount are also shot. I have to use a nut on the tensioning bolt instead of just bolting the alternator directly to the J-bar, but have just lived with it. You would think that when they go to the trouble to rebuild an alternator, change out the gut, and polish it, they would put helicoils in the threaded holes instead of leaving them stripped out.
When I was checking out the old threads, I ran a Q-tip in the hole with vasaline on it and a few circular "thread" pieces came out stuck on the Q-tip. I actually had an 8MM bolt (just slightly bigger than a 5/16") in it just to hold a ground wire, but now this bolt is going to see some serious action.
Team Owner
Joined: Jan 2006
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From: Crossville TN
The problem with those threads is not that they needed helicoils to begin with....it's that the person who changed/adjusted the belts cranked too hard on the bolts to tighten it down and stripped them out. 5/16" bolts only get about 20 ft-lbs of torque; 3/8" bolts get about 25 ft-lbs of torque [in aluminum]. Much more than that will strip the treads out of the alternator case. Your fix is still the correct one. Good luck.
