[vnarma]

Well, I had my 968 come off of Pocono East two weeks ago, and it was making a bunch of noise. Loud grinding noise. Not good. I had a friend trailer my car home, and waited for some time to check out the damage. I did the oil change, to check if there was any metal filers, indicating a spun bearing. Oil was clean. Next I thought it might be the VarioCam chain and shoes. The car has 45K miles, and these parts were on my winter update list. (Even have the parts ready to go). The VarioCam and chain were perfect. No wear or damage at all. I check further, and found a number of distrubing things.



The edge of the timing belt was frayed, which had been change some three thousand miles earlier, as where the rollers. aluminum shavings were visible in the housing as well. The problem is something unexpected, and caused lkely as much damage. The Tensioner Arm had broken off from the engine. It chewed up the belts and a number of the pulleys. Worse, it caused the engine and cam to run independently. Likely bent a bunch of valves. <img src="/forum/images/smilies/968/sad.gif" class="smilie" alt="" />











My car is being trailered down to Newton PA to Pete at RSBarn on Tuesday. The car is down for the season, but hoping to atleast get to drive her a little before it gets too cold.



Looking at the end of the stud, it looks like it had failed over time, and finally let go. The problem could have been just waiting to happen. The problem seems to come from a historic lack of lubrication on the shaft. When I had done the timing a few months back, this shaft was nearly seized. Little did I realize, the damage was done. I lubed the shaft and reassembled. Given what I know know, I would have replaced the stud. The stud costs about $60, the repair will be thousands. <img src="/forum/images/smilies/968/sad.gif" class="smilie" alt="" />



She drove great until this, and even got my person best time at the Time Trial. Glad it didn't happen on the track at speed. Atleast it failed in the paddock and not out on the track where it could have likely cause all sorts of havoc.



Don't let this happen to you.......

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[Mark]

Ouch- hopefully it's not too bad when pete gets it opened up.

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[vnarma]

Hoping it isn't too bad also. Time will tell. What else used but done while it's apart? Timing belts have to be done anyway as they were damaged. I'm havingthe Chain and followers updated to the racing variety (Had already bought them to work over the winter). Anything else while it's apart?

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[Anchorman]

Undoubtedly, Pete will advise you properly on the "while I'm in there" things to do, if any. Good luck - and OUCH!!!

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[FRporscheman]

Wow, that's terrible. I'm sorry.



I haven't seen this before. Both my 968s are doing well thankfully, and both have high mileage (168k and 220k). The 220k car has always been dealer serviced... I wonder if the dealer ever bothered to lube up that shaft. I know when I did the belts on my own car (the 168k one) I put grease on that shaft because it seemed like a good idea. I'm friggin glad I did.



Good luck.

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[Eric_K]

I almost unknowingly joined Vaino's club. I was changing the belts to get the car ready for the season and as I was working on removing the hydraulic tensioner when I noticed the pivot arm was wobbly. Hmm, why is that moving like that? So I grabbed it and gave it a wiggle and it came off in my hand <img src="/forum/images/smilies/968/ohmy.gif" class="smilie" alt="" />!!!??!!! <img src="/forum/images/smilies/968/ohmy.gif" class="smilie" alt="" /> The pin the tensioner pivots on sheared.



Judging by how it failed, it looks like it had been on the way out for a while. Having that fail while racing would have been very bad for the engine - to say the least. I was relieved to see it was easily replaceable though. $56 later, Sunset has one on the way to me.



It appears Vaino's failed at the threads while mine did at the base of the pin. Maybe these pins should be replaced as part of a normal belt service?



       

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[PorscheDude]

Interesting. I guess these cars are getting into unknown failure issues as compared to the rest of the 944 family.

At $56 that is another piece of cheap insurance, especially on higher mileage or track cars.



Although there are allot of "frugal" people who just replace the bare minimum with cheapest parts available. I foresee this "issue" popping up more in the future.

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[flash]

yup - the "if it ain't broke, don't fix it" mentality is going to upset a lot of people over the next couple of years - these cars are 15 years old - time to start thinking of them that way

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[SpeedRacer64]

[quote name='flash' post='47069' date='Feb 8 2008, 06:39 AM']yup - the "if it ain't broke, don't fix it" mentality is going to upset a lot of people over the next couple of years - these cars are 15 years old - time to start thinking of them that way[/quote]



I’m NO metal expert...but it would stand to reason after many heat cycles areas/parts that are under a fair amount of stress should be suspect.



Lucky You....

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[SpeedRacer64]

[quote name='SpeedRacer64' post='47075' date='Feb 8 2008, 09:33 AM']I’m NO metal expert...but it would stand to reason after many heat cycles areas/parts that are under a fair amount of stress should be suspect.



Lucky You....[/quote]



In addition to the aforementioned....products like Dura lube, Slick 50, etc...all came out of the space program to defend against heat/ oil starvation during extreme conditions...I’ve used several over the years and continue to do so. Added insurance and piece of mind



See back in the early days of Apollo....they were experiencing bearing failure due in part from the heat generated and boiling away the lubricant....the first to come out was the Teflon products aka slick 50...the product list is long now as most of the patents are long gone...checkout the information yourselves...come to your own conclusions...



LuKe

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[PorscheDude]

When I just did my belts, I used synthetic grease on the tensioner pivot.

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[Cloud9...68]

[quote name='smokiemon968' post='47080' date='Feb 8 2008, 10:38 AM']When I just did my belts, I used synthetic grease on the tensioner pivot.[/quote]

Did you also replace the tensioner pivot, or just grease up the existing one?



I've generally followed the "if it ain't broke, don't fix it" rule, and have kicked myself many times for the money I've wasted (e.g. the utterly unnecessary replacement of my tensioner pads and chain a few years ago - the old ones were indistinguishable from new - should have inspected them before blindly replacing them) when I've deviated from it, but the belt assembly is one area where it sounds like replacing anything that can possibly break is a very good idea. Anything else in there that anybody thinks is worth replacing? I'm going to do all the rollers, tensioner and pivot, water pump, and thermostat. Anything I'm missing? Thanks.

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[SpeedRacer64]

[quote name='Cloud9...68' post='47123' date='Feb 9 2008, 08:55 AM']Did you also replace the tensioner pivot, or just grease up the existing one?



I've generally followed the "if it ain't broke, don't fix it" rule, and have kicked myself many times for the money I've wasted (e.g. the utterly unnecessary replacement of my tensioner pads and chain a few years ago - the old ones were indistinguishable from new - should have inspected them before blindly replacing them) when I've deviated from it, but the belt assembly is one area where it sounds like replacing anything that can possibly break is a very good idea. Anything else in there that anybody thinks is worth replacing? I'm going to do all the rollers, tensioner and pivot, water pump, and thermostat. Anything I'm missing? Thanks.[/quote]



After seeing that...I don’t know were you stop...even if you purchase a new one...knowing this is a part under stress...you might further the process by having it magnafluxed...if you’re really paranoid...have one custom made out of billet steel

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[Renalicious]

This is a good thing to know! My car will be in for service again in the up coming months to get the vario cam and belts changed; I'll get them to replace the tensioner too, while they're in there. New oil pickup tune will be going in next month along with a new pan gasket.



Are new rollers a good thing to get too? Or are those usually fine?

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[SpeedRacer64]

[quote name='Renalicious' post='47128' date='Feb 9 2008, 12:08 PM']This is a good thing to know! My car will be in for service again in the up coming months to get the vario cam and belts changed; I'll get them to replace the tensioner too, while they're in there. New oil pickup tune will be going in next month along with a new pan gasket.



Are new rollers a good thing to get too? Or are those usually fine?[/quote]



Mine is in for...well a lot...and in this repair/maintenance cycle I’m having them changed...you could certainly inspect them...but why when in comparison to the cost of havoc they can cause in failing. With the understanding the mechanics and physical force applied to the belt systems...balance shafts spinning much faster than crank speed and the Vario timing...everything with respect to these systems should be scrutinized....when in doubt....change them!



Failure in any part of this system...which I'm painfully experencing....for me is at 5K for this education.

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[RS Barn]

I think this problem could become more prevelent with track/race cars. I've worked on street cars where the pivot is almost seized without breakage. The higher the RPM the bigger the problem.

Heavy decel from high RPM's could also put a severe load on the pivot. BTW, 944 Turbos don't have the same tensioning mechanism and wouldn't experience this.

I think any Timing belt allignment issues can seriously impact any threaded stud. The harmonics can do seroius damage. Balance shafts spin 2 times engine speed

I've seen all sorts of brokens studs due to this.

Pete

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