Alternator mounting bolt size

[lobf]

I noticed I wasn’t charging today, and went to pull my alternator for a diagnostic when I noticed that nothing was hooked up to it. 
 

Seems like I didn’t tighten things enough when I replaced it a few months back. 
 

Then, when I went to tighten it all back up I realized that the top mounting bolt wasn’t tightening and also wouldn’t come off- the threads were stripped. 
 

I had to grind the nut off with a Dremel to get the bolt out. Now I need a new bolt, but I’ve got health issues and I’m trying to avoid going out during the pandemic. 
 

Photo of the bolt is attached- it’s a 13mm. Does anyone know where I can order this specific bolt from? What to search for? I don’t know what you call these ones with threads just at the end. 
 

Thanks! 

[Son of Marty]

8mmx80mm according to real oem 

[lobf]

28 minutes ago, Son of Marty said:

8mmx80mm according to real oem 

Thanks Marty- does that make sense if it was loosened with a 13mm socket tho? 

[Son of Marty]

Yes, the bolt is measured by the  diameter not the head size. 

[Hans]

What do the bushings in the alt look like?

You could try lowes, ace. Most fastener stores want to sell you a box. But worth asking about one.

[stephers]

Bolts are measured by the diameter of the shaft, not the head, length is measured from the bottom side of the head NOT including the head and by the pitch of the thread

 

Thanks, Rick

[tech71]

Half of that bolt is just worn away.

Think you definitely need new bushings in the alternator attach points.

Yes, 8mm X 80mm.

You can order one and get it mailed for around 5 bucks.

https://www.boltdepot.com/Product-Details.aspx?product=6232

Better order new bushings for your alternator as well.

Hope the case isn't all wallered out, from the looks of that bolt, thats pretty likely.

The unthreaded area is called the shank.

Edited February 11, 2021 by tech71

[stephers]

Not just the rubber bushings but better look at the steel insert that go inside the rubber bushings as well

 

Thanks, Rick

[Mike Self]

Suggest that rather than replacing the mounting bushings with the OEM rubber style, get urethane bushings.  The rubber ones will turn into black goo in 4-5 years (or less, depending on your climate and how much you use the car)... the urethane bushings I installed in my '73 sometime back in the 80s are still going strong...

 

mike

[Son of Marty]

+1 on the non oem bushings you'll never hear the noise or vibration on a m10 and they last.

[Hans]

Question: does the alt have bushings or is it a solid hole? Perhaps the latter would explain the worn bolt.

[lobf]

22 hours ago, stephers said:

Bolts are measured by the diameter of the shaft, not the head, length is measured from the bottom side of the head NOT including the head and by the pitch of the thread

 

Thanks, Rick

 Thanks so much, I didn't know that! 

 

20 hours ago, tech71 said:

Half of that bolt is just worn away.

Think you definitely need new bushings in the alternator attach points.

Yes, 8mm X 80mm.

You can order one and get it mailed for around 5 bucks.

https://www.boltdepot.com/Product-Details.aspx?product=6232

Better order new bushings for your alternator as well.

Hope the case isn't all wallered out, from the looks of that bolt, thats pretty likely.

The unthreaded area is called the shank.

 

It's worn away because I had to grind the nut off the end when the threads stripped. Thanks so much for the link! 

[Hans]

If your alt has a solid hole, those bushings won't work. We're talking about the wear in the middle of the bolt. I speak from my own recent experience. 

Edited February 12, 2021 by Hans
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[lobf]

It’s a brand new alt, bushings should be fine 

[Hans]

Missed that. I now tighten that bolt one more time after adjusting the belt. It will snug up so alt won't move.