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jmercado bracket bolts broke while driving

7K views 47 replies 14 participants last post by  JDMster82 
#1 · (Edited)
So, I have an 05 k20z1 with JRSC and 3.0 pulley, I have had the SC running for about a month and had it tuned at KMOD (put down 303whp and 197wtq) today I was cruising at 80mph on the highway and my alternator light and check engine light came on. I pulled over and the car cut off, it overheated. so I noticed the belt popped off and then I grabbed the ps pump, the bolts that came with the jmercado bracket sheared off into the waterpump housing. Any idea why these bolts broke?

this is how the tensioner looks after re-mounting to the Jmercado bracket with new grade 12.9 bolts.



It seems a little off to me, maybe what caused the bolts to break. anyways, I put it all back together and torqued them down to 17ft/lbs
 
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#2 ·
What kind of bolts did you use? We're they cheap low grade bolts that you tightened to hard? I've seen plenty of that... Over torqued low grade bolts snap with to much pressure and a SC engine revving high spinning hard would cause that easy
 
#4 ·
You need Grade 12.5 (I think) allen head bolts. Only available from Jose or a local hardware store (not Lowes or Home Depot). Fastenal or similar.
 
#8 ·
ok, so update... the bolts that I originally used were 12.9 (equal to grade 8) and the top bolt sheared off and I extracted it easily. the bottom bolt head was also sheared off... but the other half of the bolt was not in the tensioner housing..?!? how does a bolt break and the other half disappear?
Vibration. Without the head to preload the bolt, it can simply slide out if there is no thread locker.
 
#9 ·
Similar situation happened to me but I was only going 2mph lol.

What I think happened, is 1 bolt got loose that holds the throttle cable onto the power steering bracket/pump and fell into the belt (belt is pretty tight) and just got completely mangled. Ruined my belt, snapped the Mercado bolts, bolts got stuck inside the tensioner. Had to get a new tensioner, belt and I used some bullshit bolts from Lowe's. I gotta look for those 12.9grade 50mm bolts.
 
#10 ·
I ended up getting grade 12.9 55mm bolts (they stuck out the other side), added anti seize and then added a lock nut on the other end of the 55mm bolts to give some tension on the other side as well. So far no issues.
 
#11 ·
Hello,

I would torque the bolts to at least twice the amount of OEM. I believe what is happening is that they are too loose.

the Bracket is then free to ocilate and eventually cause the bolt to break.

These bolts from what the others have said do not just break off. Very likely they are being bent to submission.

Also, make sure you have the right size belt. If you there is no slack on the tensioner and you are forcing it to fit with tensioner fully loaded it will leave no room for tensioner to absorb any load and the weakest point will take all the load and forces.

Hope this helps. Sorry this is happening to you. One option some have also suggested in the past is to upgrade the bolts to M10 for extra strenght.

But really I never broken the bolts and had a much heavier load due to the much bigger and heavier supercharger.

Keep us posted.
 
#14 ·
I think Jose hit the nail on the head here. We are too afraid to tighten this bolt too tight since its aluminum which will sheer the threading quite easily. Loose bolt allows the movement which will probably lead to the breaks we are seeing. This is why I added that lock nut on the other end of the bolt to give it more stability.
 
#17 ·
This is my solution that has prevented bolts being broken.

You'll see that I screwed the bolt in through the other direction and added a washer (lock nut) on the end where you are sliding out the broken part. What you are seeing here is a lock nut that I pulled back to show how I got a long bolt that extended through enough to screw it on.

 
#19 ·
it's been a month since my last bolt broke and what do you know, it broke again!!! I hate this Mercado bracket! worst experience ever!
It might be that the tensioner needs to be shaved down a little? When I got my bracket it didn't fit perfect onto the tensioner. I had to shave it down a little to make it more flush fitting.

Or maybe your belt is too tight? Idk.

If it helps at all, I have the bolts from Jose. I ended up selling the car before I installed them, if you're interested in them ($9 shipped) let me know.
 
#24 ·
Thanks for the update. I am shocked how very few people have had this issue.
Im hoping there is something I can do in the future for this rare issue. Out of the hundred's of units out there if this happened to everyone I would have removed from production... I still cant find the random cause of these few events. I think about 5 total people have gone thru this that I have been made aware.
 
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