Gixxerman88

I have a 2009 C6. I have been running the base 1500 kit for a couple thousand miles with no problems. Last night when I popped the hood to check everything out I noticed I lost 2 ribs of the 6 rip belt. Luckily there was no damage. After taking the belt off I noticed the tensioner behind the head unit had a partially broken bolt and was bent downward causing the belt to shred. Checked all other pulleys and balancer and everything is straight and tight. My question is what would cause this to happen? What size nut/bolt combo goes through the tensioner and should I replace the tensioner?

schpenxel

Can you post a picture?

Mine broke one of the bolts in that area too. Is it the same bolt that goes through the tensioner pulley, then gets a nut on it to hold the tensioner in place? That's the one that broke on mine. I replaced it with something from Lowe's and it's been fine ever since

Gixxerman88

That's the one it goes through the tensioner pulley. I will try to get some pics up tomorrow. Do you remember what size the bolt was by chance? Also were you able to find a way to get a new bolt in without removing the head unit?

schpenxel

I don't think I removed the head unit totally. I think I unthreaded the threaded rods that screw into the head unit. Once removed the whole head unit could be moved around enough to work on the manual tensioner.

That bolt 100% HAS to be threaded all the way. It cannot be a bolt the right length that isn't threaded it's whole (or almost whole) length

I had this one written down as the right one but never ordered one. In my case I bought a 4" one at Lowe's and cut 1/2" off

https://www.fastenal.com/products/details/0144569

https://www.corvetteforum.com/forums...post1588760762

romandian

somehow i think the design is wrong with the full threaded bolt. it is weak. it should be at least 12 mm.

schpenxel

I wish it were a thicker bolt for sure..and think it should be. But the obvious response would be that it works. I haven't seen many of them break..

DOUG @ ECS

Keep in mind that is not in the high tension area of the belt. The only tension on that part of the drive system is the tensioner. The supercharger is the start of the high tension area of the belt.

So I would suspect that heavy tension on that portion of the supercharger kit is from a lose belt allowing it to snap back and forth, or that bolt not being not tight.

OP we would be glad to send you a bolt if you like, PM me.

Vette97sc

Same thing happend to me too today. I have novi2000 and bracket is almost new, just drive 2500km. Yesterday i loose one rib of my belt. I check pulleys and they look fine. I change belt, one acceleration and same thing happend. Missing one rib of belt. Then i see manual tensioner pulley is not straight. I try is bolt loose or something, when i touch bolt, its snap broke. Good luck that pulley not drop while driving. I can put more pics later how bolt broke.

schpenxel

I'm interested in seeing a picture.

Xtremespeed

I think I found the reason for the bolts breaking. The pulley is supposed to be tightened to the threaded, adjustable bracket before installation on the large bracket with the slot. The problem I noticed on mine is that there is a nyloc nut that holds the tensioner in the desired position on the slot, and when you tighten that nut, the nyloc tends to grab the bolt and turn it slightly, which loosens the bolt on the threaded, adjustable bracket, which in turn puts much more stress on the bolt. I found it helps to use some loctite on the bracket threads, and I swapped the nyloc nut for a regular nut and a lock washer. It can still turn slightly, so you have to watch it carefully when you tighten the adjustable bracket down. The only reason I noticed it was, when I put another belt on and went to tighten the adjustable tensioner, it wouldn't move far enough to get the spring tensioner to the 1 o-clock position. When I looked to see why, the head of the pulley bolt had backed out just enough that it was hitting the blower bracket.

Vette97sc

Here some pics how it broke. I was 400km from home when bolt broke. I take off pulley and drive without manual tensioner. I have to move fixed idler pulley one hole up, then i get belt tight. Today i get car in garage and take 4 hours to fix tensioner. I have to take off bracket from engine, then i can lift it up and get bracket and head unit enough wide, that was not fun job.

schpenxel

That is exactly where mine broke too.

Vette97sc

I guess bolt was half cut and then pulley look like this.

schpenxel

Yep, pulley on mine did the same thing..

However, since replacing it and using a laser alignment tool to correct pulley alignment I haven't had a problem since.

My theory is when the belt jumps off it goes tight as hell for a split second and puts extra pressure on everything. If this bolt is the weakest link (and being a fully threaded bolt, it probably is) then that is what would break

LD85

Wow, not good and it should be preventable, what grade are the bolts? they look like all-thread

schpenxel

They have to be fully threaded with the way the tensioner is designed.

Pretty sure they're grade 8

Arctic Vette

Yup they are grade 8 = 6 radial, grade 5 = 3 radial Grade 2= 0 mark. Been hearing a lot of these breaking..

neutron82

there have been quite a few people with the same thing happen... good thing their design makes belt changes easy

schpenxel

lol true

I still think it's from a combination of misaligned belts and having this bolt overtightened. Belt starts to jump off, goes tight as hell and this is the weak link that snaps.

The manual tensioner is on the "loose" portion of the belt drive, so it shouldn't need a ton of force to keep it still.. the fact that these are breaking makes me think the belts are going super tight for whatever reason.

Although it cost me a tow.. I'd still rather this break vs. a tensioner which costs a lot more

Xtremespeed

I know my answer seems to be falling on deaf ears, but you guys should look closely at that bolt when you tighten the nyloc nut that holds the adjustment. Before that nut is even tight to the washer the nyloc tries to turn the bolt which loosens it ever so slightly. It's not much, but only takes a couple of times for it to loosen just enough so the pulley is no longer completely tight against the bracket. When the pulley isn't tight, it puts a much higher load on that bolt. I'm confident, at least in my case, this is the problem. I caught mine before I broke the bolt.