Broken tensioner pulley

3 months ago I took my 2007 Cayman S to the dealer to fix a check engine light, they called me recommending changing the belt due to age and being proactive I accepted. My Cayman has only 20K miles. After driving less than 200 miles after that service I hear the the belt break so I towed it back to the dealer. Their diagnosis is that the tensioner pulley broke and caused the belt to wear out. I am not ruling out a wrong belt or installed incorrectly by the technician. I see one side of the belt wore out greatly after rubbing on the alternator and eventually locking up and causing the pulley to break. Does anyone support my theory or the dealer's diagnosis that the pulley broke and caused the belt to come off. Can someone share your thoughts on how this could have happened? I am attaching photos of the aftermath.

I'm in the middle of a waterpump and thermostat replacement and so I removed my belt today. Honestly, I don't know how you could install the belt wrong and have it operate for even 1 mile. But that doesn't mean that it's impossible for someone to damage the idler pulley I guess. Although it really doesn't require any precision to engage the pully in order to gain necessary slack. The only thing that I can think of that changing the belt could damage is if the belt was too long or too short? Or if the belt was damaged and that led to it breaking, that could definitely take out the idler pulley or one of the other pullys.

I am not sure if there are differences between the 987.1 and 987.2 belt assembly. On the 987.2 one of the key components in maintaining the tension is on the belt tensioner - (looks like a small absorber). I've had mine changed before. The pulley wear would be inspected at the same time and if there are already wear marks the pulley should be changed for good measure. A full service on the belt system would include a change of the above mentioned components + checking the water pump and anything else in that area. You can check out my earlier post with pics that show you normal (to me) wear. 9A1 100,000 Kms (60k miles) Water Pump, Belts and... it has been a few months of hunting down increasingly worrying sounds coming from various parts of the car. some intermittent, some there in the form of pulsing, tapping or grinding. thankfully with a good tech from a local indy, managed to get the source of the sounds traced to the water pump... www.planet-9.com Jamie, I couldn't ascertain if the job was done at an authorised/experienced Indy but I do have a similar view to snakebitten....assuming the right parts (and quality) its not easy to mess up this job of installing the belt.

Did you simply have the belt replaced or did they replace the pulleys and tensioners as well? It’s pretty common to do them all as one maintenance procedure. if you only replace the belt it is quite possible the tensioner decided it was time to give up the ghost and that resulted in the broken belt. It would be very difficult and uncommon to install the belt incorrectly. If you skip a poly it certainly won’t fit properly and if you have it twisted, that should be apparent as soon as the engine is started.

Thank you so much for your feedback to both. The belt service was done at the Porsche dealer but they didn't change the tensioner or any other components, they now say they didn't see a need for replacement... my response is if they recommended changing the belt because of age why nor service the whole system? Thanks for clarifying about the unlikeliness of assembly error, I had not ruled it out. If I interpret correctly this is an unfortunate coincidence the dealer changed the belt and shortly after the tensioner failed. I very much appreciate all the feedback and if someone else has any other ideas or thoughts about this problem I would like to hear.

I'm not sure we could prove the tensioner failed first, but it's worthy of consideration. 20,000 miles is fairly low. But then that's true for the belt too. Chicken/egg A belt failing can wreak havoc on any component involved in the ensemble. And vice versa. Could the belt be a factory defective belt? Or could the belt have been nicked or damaged during install? Did the tensioner pully (1 of 3) coincidentally fail at 20k? I'd love to go back in time and not even replace the belt and see if the car would be just fine currently. Who knows.

When I did this job on the 986 , I discovered that the internal bearings within the rollers were not only common at NAPA but very easy to press in and out. Next person who is going to throw one out should verify whether that is still true. Brand new bearings were super cheap and the exterior roller portion unremarkable in wear. If this is still fact, then we only need to buy the tensioners and replace the internal bearings on a schedule of our own choosing.

I would guess the tension from the belt being new caused the tensioner to fail. 20K is low for all of this to happen . But 15 years is old for rubber , so may be a combination of factors. I would at least ask for a break ( pardon the pun) on the service and parts , I mean you could get ugly and say it was their fault ...but then that could go south as well . Can you cross check the part number with the new belt, make sure its the right one? Was your old belt worn on one side or the other ? One other thing , did you hear any warning signs in the 200 miles? Usually a tensioner going bad will make a racket ?

Hi, only the belt was changed...I didn't hear any warning noises of a possible part wear. The engine sound was smooth, no squeak or binding was noticed. I also wish the dealer had not changed the belt. The dealer does not wsnt to take any responsibility and they lock on the diagnostic of broken pulley. I do recall the conversation with the service advisor was just considering age, he never mentioned wear or noises. I cannot find any logical explanation for the pulley to break in pieces and seeing so much wear on one side of the belt. This is just an unfortunate coincidence. I have been trying to find any part number on the actual belt. I am not sure how i can tell if the correct belt number was installed.

Hi, there were absolutely no warning signs. Only the loud pop and flapping when it happened. The car speed was about 55miles when it happened. The old belt i didn't see, it was removed at the Porsche dealer The torn one i recovered from them. Is there a way to confirn the belt part number?

As mentioned earlier, I removed my belt to do the waterpump replacement and although the belt looks healthy to my eyes, nor do I hear any noise that I would consider an alert, I ordered a new belt. I did not order the tensioner "kit" because everything feels smooth and sturdy to my hands. However, Boris posted above an inexpensive option compared to the $500 kit and I'm thinking it might be prudent to swap out bearings if indeed it is easy to fetch them. My car is is about the same age as yours and now has 50,000 miles. Since the waterpump suddenly let go, and without any warning, I'm addressing anything and everything related to the coolant loop. Hope things work out for you.

I'm curious, would you mind telling us the cost ? Thanks ~

In thinking about this - the tensioner pulley is plastic. The failure of it so soon after a belt change to me indicates it was damaged during the belt change. Since the tensioner has to be "relieved" to install a new belt, the chance of a slipped tool damaging it causing the rather quick failure seems much more likely than it decided to fail by itself right after a belt change. I'd continue going after the dealer on this. You may want to escalate this up the chain of command - the actual service manager would be my next step (not a service adviser..) and if that didn't work, the business manager (who runs the whole place.)

Ugh! I hate hearing stories like this! I have 76k miles on my 2006 boxster s and I changed only the belt about 5k miles ago. Never changed the pulley. It’s super doubtful that the pulley just fails like that. I agree with others if that the belt was installed incorrectly you’d almost know immediately with noises coming from that area. It’s not like a typical car where you can immediately see the engine bay unfortunately to see what’s going on in there easily after a belt change. I would ask to escalate it and ask them to work with you on the repair costs to possibly split them

The dealer cost is 4000 dollars, they wanted to replace the alternator and the broken pulley. I have decided to do the work and so far in parts I have spent $500. I am replacing all three pulleys and a new belt. There's nothing wrong with the alternator . This Porsche dealer in Atlanta is very dishonest