Generator/Alternator top bolt stuck

Hi All,

I'm having a problem with the top alternator bolt for my 2009 DC Offroad with ~131K miles. My project was to replace the belt/pulley tensioner assembly (bearing only change didn't work) to eliminate noise when the A/C is on.

I managed to get everything disassembled and have replaced the old pulley tensioner part with the new one. Now I'm attempting to reassemble in re verse order.

The compressor bolts went in with no problem but the alternator top bolt won't thread/seat properly into the hole. The bolt seems to seat OK at first but when tightening it begins to grow tighter and tighter. The bolt looks OK, but you can clearly see where something is rounding off threads (see pics):




I don't want to force anything or overtighten the bolt because I'm afraid of it snapping off or causing more thread damage. Here are the options I see:

• Use a metric thread restorer to repair/remove debris from the top bolt hole + get new bolt(s)
  
• Use a metric tap to fix the bolt hole threads + get new bolt(s)

Does anyone have suggestions?

I found this tool on another thread - any good for a problem like this?

$44 Lang Tools 2584 15-Piece Metric Thread Restorer Set, Black , Gray

https://www.amazon.com/Lang-Tools-2...t=&hvlocphy=9010826&hvtargid=pla-450116451264

Thanks!

 

It’s hard to tell by the pictures.
But yes, thread chasers are always good to restore/clean threads.

You might have to take the bolt out of the bottom, and hang the top bolt first.
Or at least back the bottom bolt out as far as you can to get the top to line up.

Like I said, I can not tell exactly if it’s a bolt or mounting issues from the pictures.

 

I would remove the alternator, blow out the bolt hole, use a 90 degree pick to lightly scrape the bolt hole threads of foreign material, buy a new correct thread size bolt to try and thread into the hole to test/clear up the bolt hole.
For what its worth I use my thread restorer set way more then I use my tap/die set.

 

Thanks for the quick reply TnShooter! It is hard to see but there is one thread "valley" on the bolt that is showing shiny new metal that goes nearly 360 degrees around the bolt shaft. Turning the bolt just gets harder and hard - which is why I stopped tightening things up. I've battled with this for a couple of hours and no matter what I try the top bolt just won't align correctly or seat all the way into the bolt hole. I think you're right - I'm going to locate a thread chaser kit and see if that will clear the hole up enough in addition to getting couple of new bolts.

I thought the tensioner replacement was bad enough.

 

Sometimes, when I remove a bolt. If it feels tight when backing it out, I’ll run it back in, and then out, as I take it out.
I’ll do this the whole way out. Aluminum can get “sticky” and fight you.
I don’t know the right term, but I’ve had it happen before.

Obviously, this isn’t an option now. Since the bolt it out.
Was it “tight” the whole way out?

 

Turning force increases (too much) as the bolt is tightened more and more. Same when backing it out - it's quit tight until most of the threads are backed out. Next step is to clean out/restore the threads and try new bolts too. Hopefully a thread restorer will clean things up enough for a new bolt to seat the whole way.

Any recommendations on a good metric set of thread restorers vs. what I found in another thread? Joeyv141 - what do you use?

 

I use this, but most hardware stores have a generic kit.
The generic kits are fine, they just don’t last if you use them a lot.
https://www.searshometownstores.com/product/Craftsman-971-2750-48-pc-SAE-Metric-Thread-Restorer-Kit

 

I'm a professional mechanic so I own a snap on master set, I think it was around $300-$400, definatly not worth it unless you use it professionally. I dont know what the thread pitch is for the bolt in question but I imagine the Lang set you mentioned would work fine, I've got a few Lang tools and I've been happy with them.

 

Is the bottom bolt loose enough to where the alternator has some slight movement to it? It's not tightened down completely or torqued to spec, correct? If it is, it may not be allowing the alternator to move enough for the upper bolt to 'find' the threads.

If you don't have a metric tap and die set, try a wire brush on the bolt to clean the junk off the threads.

 

BadAndy10 - I tightened the bottom bolt just enough to keep the alt. attached to the engine block boss (after pressing the nut sleeve back down flush with the inside face - this was a serious PITA too). I did NOT tighten to spec. Thought this would help keep things better aligned but apparently I need to insert the top bolt first.

New procedure:

1. Get new bolts
2. Use a thread restorer on top bolt hole
   
3. Check for bolt travel after restoring threads
4. Install top bolt first, then bottom, finish alt reinstall

Thanks all for the product recommendations and help!

 

That the same plan of action I’d take.

 

You don't need a whole kit, most of these bolts are either 8x1.25 and 10x1.25

 

Thanks for the info @b_r_o ! Update: found the part # from Toyota: 90119A0146 As you indicated, I'm pretty sure this bolt is 10x1.25 but there is no pitch information on the parts description. Caliper measurements:




Part number searches on rockauto.com or napaonline.com don't turn up results so I had to order from a Toyota stealership. I even called a dude @ Napa and gave him the Toyota part number - no dice. Anyone know of a substitute or more generic bolt via Rockauto or another vendor?

Also dumb question for y'all - it appears the bolt hole is threaded all the way through the front engine cover into the block - I used an air duster with a long tube to try and blow things out. When using a thread chaser/restorer/tap is it best to attack this problem from the front or rear of the bolt hole? In order to get to the rear hole I'll have to take apart part of the top of the engine and remove the black support brace which isn't a big deal but I don't want to generate any unnecessary work. Any thoughts?

Cheers - flu33ys

 

1.25 is the thread pitch

You don't need a new bolt, you need more threads inside the aluminum engine block

That's what the tap is for, to clean things up in there and try to get some purchase on the threads

 

Could also run a die over that bolt in case some of the lead in threads are just a tad buggered. Or use a thread file.

 

^^^ this or at least take a stainless steel brush to the threads.

 

Problem fixed: ordered an M10-1.25 thread chaser and gently cleaned things out. It took several attempts to get full travel for the new bolts but they torqued up to 43 ft lbs quite nicely. Here's a good tip: for the upper generator bolt hole make sure to blow out debris from the back - the hole tapped goes all the way through the block but it appears NOT to be fully threaded. Thanks all for the tips and info. Gotta love TW!

 

FYI... When measuring the length of a bolt with calipers or a ruler you don't measure overall length like in your photo but from the bottom of the threads to the bottom of the shoulder. You don't measure the top hex portion where you put your wrench. Like in this photo:. https://images.squarespace-cdn.com/...1609373976603-1EZYI2MGM5Z1V7I9KUQC/bolt-1.png

Looks like a 60mm long bolt (lengths are usually round numbers).

And I'd recommend you buy a thread pitch gauge for metric and SAE...very handy to have in a toolbox.