GTS Cam broke
02-07-2012 | 04:53 PM
#62
Nordschleife Master
Joined: Dec 2004
Posts: 6,164
Likes: 5
From: Guelph, Ontario, Canada
Here's a closer look at the cam gear. Obviously the bolt has been loose in the past otherwise the key wouldn't be torqued like this. I find it odd though that the bolt had good torque on it when I checked it the other day. Makes me wonder if it was found loose like this in the past, re-torqued w/o a proper inspection. This is not due to a cam shaft defect.
There is a slight bit of rust, but not at any of the break points on the retainer. Just the mating surface between retainer and cam gear.
We can all speculate as to the cause, until I get the engine torn down we won't know for sure. There is a chance the parts are fine with the tensioner arms/bushings/belt/pump and Greg is correct about this gear/bolt.
There is a slight bit of rust, but not at any of the break points on the retainer. Just the mating surface between retainer and cam gear.
We can all speculate as to the cause, until I get the engine torn down we won't know for sure. There is a chance the parts are fine with the tensioner arms/bushings/belt/pump and Greg is correct about this gear/bolt.
Yes this is what I do for a living (Mechanical engineer)
02-07-2012 | 05:21 PM
#63
Former Vendor
Joined: Feb 2005
Posts: 15,230
Likes: 2,489
From: Anaheim
Here's a closer look at the cam gear. Obviously the bolt has been loose in the past otherwise the key wouldn't be torqued like this. I find it odd though that the bolt had good torque on it when I checked it the other day. Makes me wonder if it was found loose like this in the past, re-torqued w/o a proper inspection. This is not due to a cam shaft defect.
There is a slight bit of rust, but not at any of the break points on the retainer. Just the mating surface between retainer and cam gear.
We can all speculate as to the cause, until I get the engine torn down we won't know for sure. There is a chance the parts are fine with the tensioner arms/bushings/belt/pump and Greg is correct about this gear/bolt.
There is a slight bit of rust, but not at any of the break points on the retainer. Just the mating surface between retainer and cam gear.
We can all speculate as to the cause, until I get the engine torn down we won't know for sure. There is a chance the parts are fine with the tensioner arms/bushings/belt/pump and Greg is correct about this gear/bolt.
Yup.
That's the problem.
The bolt was slightly loose, allowing the pieces to work against each other. As I said, after the break occurs and the two broken pieces are separate, the broken off "nub" will rotate on the end of the remaining camshaft, until the "high spots" interfere. That will make the bolt tighter. The "shiny" area is actually where the two pieces rotated against each other, until the "high spots" grabbed and held everything in place.
02-07-2012 | 09:42 PM
#64
Rennlist Member
Joined: Apr 2006
Posts: 35,700
Likes: 503
Yup.
That's the problem.
The bolt was slightly loose, allowing the pieces to work against each other. As I said, after the break occurs and the two broken pieces are separate, the broken off "nub" will rotate on the end of the remaining camshaft, until the "high spots" interfere. That will make the bolt tighter. The "shiny" area is actually where the two pieces rotated against each other, until the "high spots" grabbed and held everything in place.
That's the problem.
The bolt was slightly loose, allowing the pieces to work against each other. As I said, after the break occurs and the two broken pieces are separate, the broken off "nub" will rotate on the end of the remaining camshaft, until the "high spots" interfere. That will make the bolt tighter. The "shiny" area is actually where the two pieces rotated against each other, until the "high spots" grabbed and held everything in place.
The level of expertise we have here is just amazing. I bet there isn't a thing with these cars that someone else has not seen.
I'll be pulling the engine starting mid next week and I'll keep a running documentary on what's found and how the rebuild goes. As always, feel free to comment but don't get butthurt if your thoughts go unheeded.
02-07-2012 | 09:57 PM
#65
Rest in Peace
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From: Bird lover in Sharpsburg
I love this community.
The level of expertise we have here is just amazing. I bet there isn't a thing with these cars that someone else has not seen.
I'll be pulling the engine starting mid next week and I'll keep a running documentary on what's found and how the rebuild goes. As always, feel free to comment but don't get butthurt if your thoughts go unheeded.
The level of expertise we have here is just amazing. I bet there isn't a thing with these cars that someone else has not seen.
I'll be pulling the engine starting mid next week and I'll keep a running documentary on what's found and how the rebuild goes. As always, feel free to comment but don't get butthurt if your thoughts go unheeded.
02-07-2012 | 10:35 PM
#66
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Joined: Oct 2004
Posts: 2,910
Likes: 317
From: K-town, Germany
For the tension light to keep coming on and going off, would it have been caused by the bolt loosening and causing slack and then catching itself and tightening back up? Or is that something unrelated like maybe the conti belt stretching?? No kidding, if it wasn't 10 degrees here, I'd be in the garage right now checking my cam gear bolts!
02-07-2012 | 10:45 PM
#68
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Joined: Oct 2004
Posts: 2,910
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From: K-town, Germany
Okay, so I just re-read this again, then it was after the break "the broken off nub will rotate on the end of the remaining camshaft, until the "high spots" interfere. That will make the bolt tighter" So if that only explains the after the fact how the bolt got tight again when Sean checked it, what caused the light to go on and off? Was it not a loose bolt loosening and tightening??
02-07-2012 | 11:02 PM
#69
Three Wheelin'
Joined: Nov 2008
Posts: 1,675
Likes: 4
From: TEXAS
The bolt was slightly loose the whole time, either from factory or from the last timing belt job, until the cam broke from accelerated fatigue due to the loose bolt. The previous mechanic could have loosened the bolt by accident during the last timing belt job.
A simple thorough inspection from the mechanics would have caught the problem and prevented this failure.
The bolt tightened back up after the failure happened like I explained on the last page.
A simple thorough inspection from the mechanics would have caught the problem and prevented this failure.
The bolt tightened back up after the failure happened like I explained on the last page.
02-07-2012 | 11:27 PM
#70
Rennlist Member
Joined: Oct 2004
Posts: 2,910
Likes: 317
From: K-town, Germany
The bolt was slightly loose the whole time, either from factory or from the last timing belt job, until the cam broke from accelerated fatigue due to the loose bolt. The previous mechanic could have loosened the bolt by accident during the last timing belt job.
A simple thorough inspection from the mechanics would have caught the problem and prevented this failure.
The bolt tightened back up after the failure happened like I explained on the last page.
A simple thorough inspection from the mechanics would have caught the problem and prevented this failure.
The bolt tightened back up after the failure happened like I explained on the last page.
02-08-2012 | 02:23 AM
#73
Former Vendor
Joined: Feb 2005
Posts: 15,230
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From: Anaheim
02-08-2012 | 07:07 AM
#74
Thread Starter
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From: In a tizzy
Kinda waiting for Sean to check the condition of the passenger side before deciding the extent of how deep down the rabbit hole I can go.
Till then I'm bugging a LOT of people with questions. Think I'll start a thread.
Till then I'm bugging a LOT of people with questions. Think I'll start a thread.
02-08-2012 | 11:26 AM
#75
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Joined: Jan 2012
Posts: 1,158
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From: Oklahoma City, Oklahoma
You would be correct there. The car lost power then as the snap happened we heard a distinct grinding noise. It was the cam gear hitting the timing belt cover. Then the car died and we rolled to the side of the road. I wasn't sure what the grinding was because I expected to hear pinging or something like that. It didn't click till we saw the broken cam and the wear marks from it hitting the cover.