OK, so a little background info first. I've got a 2008 G37S, was driving home from work on Friday and the serpentine belt broke and stranded me on the side of the road. I'm not exactly sure what happened, but it looks like the idler pulley somehow loosened and the belt got wrapped behind it. The pulley was pulled out about an inch and was angled slightly, so it was clearly messed up.

Once I got all the pieces of the belt off and removed the pulley, the bearings in the pulley had broken and it was ruined. Not a huge deal, the idler pulley isn't too expensive. But since I have bad luck, the hole the pulley bolts to is stripped. So I have a new pulley and belt, but I can't get it back on. The bolt starts to go in for about 1mm, but then it starts angling and won't move any further. Am I SOL with this? Is there anything I'm not thinking of that can be done? The only thing I can think of is taking the front of the car off and retapping that hole, which I'm definitely not comfortable doing.

 

you'll need to put in a heli coil or some type of thread repair once the hole is tapped. It will be strong. do it carefully.

 

That's where I figured things were heading. I've seen Helicoil used before with a stripped spark plug socket, so I'm pretty sure I can do that. I'm more concerned about having to take everything apart to be able to get to where I need to be drilling. I don't remember how big the tools are for the Helicoil, but I doubt I'll have enough room without taking things apart.

 

I managed to very carefully run a tap through the hole, and I am able to put a bolt in tightly. So I think I saved myself the trouble of having to take the bumper and radiator off. The original bolt is bent slightly, so I need to replace it.

My question now is whether I need to get a special bolt or not. I have found a grade 8.8 bolt at the hardware store that is a direct replacement size-wise, but I don't know how much stress the bolt is going to be under. I'm assuming it's going to be fine.

 

if the bolt is a true grade 8, you'll be fine. It should cost a lot more than any other bolt you've purchased before, have dashes on the head designating the grade, be black in color... the hardware sounds good, just be sure the tapped part is good...

 

It's a class 8.8, which is equivalent to SAE grade 5. I think class 10.9 is the metric equivalent of grade 8. Do you think it will at least hold for a small amount of time? I couldn't find a 10.9 locally in the right size, I'm going to have to order it. If I temporarily use the 8.8 while the 10.9 is on its way, I can return the car I'm renting immediately. I know I'd be rolling the dice a bit, but now that I have the pulley in and the belt on, it doesn't seem like there is an enormous amount of stress on the bolt.

 

Bolt Depot - Bolt Grade Markings and Strength Chart has info regarding strength of the bolt. I'm not an expert by any means so realistically use all of what I've given with that knowledge and a grain of salt...