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99 Crank Pulley Bolts - shearing

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#21
callumhay

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I'm wondering if excess tension on the water pump/alternator belt could be an issue. That's something that's likely to be quite variable among the cars. It's easy to make it really tight with the tensioning mechanism on the alternator. It's just a thought and at first pass on this I thought that maybe the water pump wheel might suffer first. But the harmonic balancer is much heavier and I'm sure the centrifugal force on that thing at 7500 rpm is massive.
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#22
Steve Scheifler

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In some highly stressed engineering environments, we only use bolts for a single use. Once they are tightened to the specified torque, they elongate and are not viable as a re-use item. Does this apply in this environment?


But TTY is an intentional tightening to the point of permanent stretch. If using recommended torque for the bolt, that should not apply. But if people significantly over torque "to be safe" it may very well apply. I still wonder if this really does occur without the bolts loosening slightly first.
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#23
callumhay

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I'm wondering if excess tension on the water pump/alternator belt could be an issue. That's something that's likely to be quite variable among the cars. It's easy to make it really tight with the tensioning mechanism on the alternator. It's just a thought and at first pass on this I thought that maybe the water pump wheel might suffer first. But the harmonic balancer is much heavier and I'm sure the centrifugal force on that thing at 7500 rpm is massive.
Cal

#24
Ron Alan

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May have no relation but I have seen an alternator "freeze" and burn the belt to shreds...could the load of an Alternator put stress on the pulley/bolts over time? Asking from a lack of knowledge perspective  :wacko:

 

Like Steve...I also feel something has to get loose first! 


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#25
davew

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I have never used a Mazda preslotted timing wheel. I slot my own. And it still happens. So the issue is not the Mazda wheel.

 

I am not an engineer, but I am fairly confident that the issue is caused by vibration. Slotted wheels, Mazda wheels, big bolts, old bolts, ARP bolts (per my buddy Ralph) all seem to break.

 

My suggestion, new bolts on regular basis.

 

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#26
FTodaro

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Having been there on this problem, i made up a spare's kit that i keep in my trailer, it included a harmonic balancer, bolts, crank button (thing it bolts too) and crank Keyway), timing plate and a new belt.

 

I try to put an eye on it before every weekend, but i am ready for it.


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#27
ChrisA

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May have no relation but I have seen an alternator "freeze" and burn the belt to shreds...could the load of an Alternator put stress on the pulley/bolts over time? Asking from a lack of knowledge perspective :wacko:

Like Steve...I also feel something has to get loose first!


It's possible that the load placed on the pulley by the alternator and an overly tight belt are contributing factors. Especially, since probably all of us have ditched the Power Steering pump, which provided a countering load to the alternator on the pulley. Though, I can't remember if mine broke before or after I removed the Power Steering. :scratchchin:
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#28
RazerX

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Well in this case, I know the belt was not over tightened, if anything it was a little lose.  Start up belt squeal.  Perhaps that induces some vibration as well.  What is odd, is that we all know these motors with OEM bolts can last over 100,000 miles without this happening.  So my reasoning is the higher RPMs.  Has anyone 'balanced' the pulley?  Is that legal?


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#29
Mark McCallister

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What year did power steering and A/C become standard?  Perhaps the combination of the lack of the second belt and high RPMs?


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#30
Steve Scheifler

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I was working on one today with a timing wheel that was slotted manually some years ago. I found that the slots had not been deburred. Is it possible that in some cases this prevents proper mating of the surfaces or correct torque and leads to the bolts loosening enough for the pulley to start leaning on them?
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#31
RazerX

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When i removed the studs out of the crank button, I had to use pliers.  Meaning the loctite was still holding them in, but I do agree that losing or cyclical tension may be the culprit.  But in my case the were not lose and backing out.


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#32
SaulSpeedwell

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I knew a guy whose torque wrench read 30 ft-lbs low and his tire pressure gauge read 8 psi high.  That guy had lots of problems.  Something to check.


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