2006 Accord V6 Went 220k miles before the first bolt broke. it broke off almost flush with the head, there is ZERO room in there to get any regular tools. Had a hell of a time getting the bolt out. Ended up having to drill and heli-coil it. Ordered new tensioner, bolt from Honda. Got it all back together, then BANG. Tensioner blew up again, bolt sheered off. Maybe 1000-2000 miles later. I thought maybe I didn't tighten it all the way and it was vibrating?

I ALSO found that the last time I replaced the tensioner, Honda changed the design so you have to notch the timing cover so the tensioner can sit flat. SO I thought AHA! That's it. It was sitting a a slight angle, and with the tensioner pressure it broke the bolt. I ordered another tensioner and a GRADE8 bolt, did the proper notching, etc. Made the sure the bolt was tight, even RECHECKED it after 200 miles or so. Still tight.

Then today I hear high pitch rattling. The bolt is literally spinning/vibrating. It broke off AGAIN, but I caught it before it could destroy the tensioner. WHAT IS GOING ON? Help!

 

Somehow I missed this. Use a straight-edge on the various pulleys and see if any are out of line. You may also want to spin each pulley if possible to see if one is wobbling.

Some shops have a laser system to check pulley alignment.