2003 Mazda 6 2.3 DOHC, keeps breaking idler pulley bolt

Glenn Owner/Technician Texas Posted   Latest  

Hello DN members,

I have a fellow tech who called me with a repeat engine idler pulley bolt breakage problem. The bolt that keeps breaking is the long one (his description). He has replaced it 3 times, once with used and the other two times with new (OE). He has had multiple techs look at it and everyone is baffled. I have not found any TSB's yet, but still looking. A new pulley (OE) was installed the last time around. The belt has also been replaced a couple of times due to damage.

When it is running there is no belt vibration and all other pulleys are in good condition and mover freely.

Has anyone had this issue before? The vehicle broke down 4th time (same reason) this afternoon and he called me for ideas.

If anyone has run into this problem with this vehicle design before, your help would be appreciated.

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Tim Owner/Technician
Virginia
Tim
 

Hi is it possible the alternator was replaced and does not have an clutch pulley (OAD)

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Marlin Technician
Oregon
Marlin
 

I first thought of the OAD also.

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Glenn Owner/Technician
Texas
Glenn
 

Thanks Tim, I will have to check into that, not sure if this had an OAD setup.

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Marlin Technician
Oregon
Marlin
 

Another possibility is that the hole is cross-threaded, causing strain on the bolt.

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Maynard Technician
Ontario
Maynard
 

We had a Ford focus with a very similar problem. The fix seemed to be to install a new front engine/ timing cover. And new idler and new bolt. Somehow if the mounting surface was even slightly burred or grooved in the cover it would not allow the idler to sit 100percent squarely. And this started too much side load on the actual bolt

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Glenn Owner/Technician
Texas
Glenn
 

Thanks Maynard, I plan to be checking it myself over the weekend and I will look at the cover carefully. The location of the pulley is in a difficult place to begin with, but I think a flex camera May provide a better view.

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Nick Service Manager
Indiana
Nick
 

I've had this happen on a Focus as well, I couldn't visibly see anything wrong with the cover but it snapped 2 of those bolts within a month. A new cover fixed it

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Don Diagnostician
Tennessee
Don
   

That's a weird one, Glenn! Like others I'm wondering if any work was done to one or more belt-driven components prior to the breakage of the original bolt. Was the idler pulley removed for some reason and the bolt over-torqued? Could the new drive belts be too short (whether aftermarket or dealer-sourced)? Could a new tensioner be applying excessive tension? Could a pulley on another component…

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Glenn Owner/Technician
Texas
Glenn
 

Hi Don, In a short time have done a lot of digging on this subject and there appears to be a design flaw. Many replies on several sites, including this one, suggest replacing the timing cover. Simply installing a new pulley and bolt just does not work for very long. If I understood my fellow tech correctly, this will be his 4th time for this problem. His wife loves the car, so he wants to fix…

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Glenn Owner/Technician
Texas
Glenn
 

Hi Don, To answer what other component have been changed? The AC compressor and front “nose” motor mount was replaced last year, but the problem existed before that. All other components are stock from what I can tell. Pulley and belt alignment has been checked multiple times by him and other fellow techs with no issues found. There has been no excess vibration present. He is going to check…

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