Rep Power: 0

2006 Civic, 2 door, Automatic transmission, 250k miles, multiple owners, I have had it for 6 months

Twice in two months, the accessory belt tensioner bolt has snapped off in the head. In both cases, the break causes the tensioner to shift and rub against the belt idler pulley. The pulley then grinds down on the tensioner. In addition to making a really loud noise, if left alone I am pretty sure it will grind the tensioner in half.

In the first instance, we had to weld a nut onto the broken bolt shaft that was stuck in the block. The location of the bolt makes it impossible to get a bolt extractor in because of the close proximity to the frame (90 degree angle). Pulling the engine out to be able to get to it would probably work as well, but is way more time/energy than it is worth. In reading about a similar issue on Honda Odessy forums, several people said that Honda's technical fix is to replace the engine block. That's a ridiculous fix for a 20yo car with 250k miles on it (or any other situation).

I am trying to root cause the issue so that it doesn't continue to happen. I bought two bolts ($3 each online instead of $30 each at dealership) last time. Both come in Honda packaging and say OEM part. What I can't figure out is what is causing a torque twist to break the bolt off in the exact same place (sheared bolts are exact same broken spot on threads). In theory, it seems the tensioner should be in line with the other accessory pulleys, so sideways twisting/torque on the tensioner (therefore bolt) should not be taking place.

It did start happening after I installed a new alternator. Could the pulley on the alternator be offset just enough that the belt is pulling the tensioner sideways? Any help is appreciated.

 
Rep Power: 222

Could be fake bolts

 
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I had never eve considered that. How would I know, unless I buy from the dealership at $33 per bolt?

​​​​​​I get that dealer markup is going to be there, but 10x what a standard bolt would be?

The ones that I bought were in honda package, but I guess that could just be a fake as well.

 
Rep Power: 222

They fake the packaging as well.
you could go to a bolt supply store and see if they can get you a bolt with the same specs

 
Rep Power: 0

I went to Fastenal and got a replacement bolt. It's 1mm longer, but that shouldn't be a problem. The guy there said "this one won't break. I don't know what else might happen, but it won't be a broken bolt." It's going to warm up over the next couple of days, so I am going to extract the old broken off piece and put the new one in. We'll see how it goes.

BTW - the Fastenal price was $5.50 for 10 bolts.

 
Rep Power: 222

Good luck