J.O.

I have been reading the endless number of belt threads and also alternator threads tonight and I want to ensure I am not missing anything.

About 10 minutes before my alternator belt tore in half I was hearing a clattering noise then a higher pitched whirring. I stopped and looked in the engine and couldn't discern the exact location and since I was almost home I kept going, figuring I would investigate more at home. Then a couple of minutes later I heard the belt go out. All the ABS and brake lights immediately came on, by then I was only a few minutes from home and easily made it home. The noise immediately went away with the belt failure. At home I took a look and found the broken alternator belt and could also see that the fan belt and A/C belt are partially inverted so you see the "teeth" on the outside of part of the run. After it cooled down I tried spinning the alternator shaft and it seems to spin smoothly.

I purchased the 1996 C4S before the summer with 108k miles on it and have driven it a couple of times a week and only put a couple thousand miles on it. Right before I purchased it the PO had his local Porsche dealer replace the Cooling Fan (it was hitting the housing) and they changed out the Alternator (alternator bearings faulty), belts, and updated the pulleys (seized on shaft), as well.

Obviously I will be replacing all the belts but I wasn't sure if the noise I heard before the failure was something more that caused the failure. From reading I am guessing this noise was either the new alternator failing (seems common) or one of the bearings failing.

Should I replace the belts first and see if the noise returns? Or is it definitely something more and I should go ahead and pull the alternator and bearings?

P-daddy

Do you know if the replacement alternator was Porsche or reman? To start grab the alt shaft and spin the fan to check for odd noises. Does it spinning freely? Next hold the fan and spin the alt shaft. Any weird noises? One more, grab the alt shaft and try to move it up and down then laterally. If there's play, most likely the alt bearing is bad. This is just to start and assuming you hadn't replaced the belts yet.

J.O.

I assume since the work was at a Porsche dealer that the alternator was OEM. The receipt just shows a part number, description and price.

Fan spins clean and smooth.
Alternator shaft spins smooth with fan not moving or with.
Alternator shaft feels solid and doesn't have any play.

While I am at it, I think I will move to the RS single belt system since that seems to be a popular and hopefully more reliable setup. I live in the mountains in a resort area and rarely spend time idling in traffic so I don't see an issue with a slower spinning alternator.

P-daddy

I'd reinstall the alt belt and run it to see if the noise comes back.

Do you DIY? This job is not complicated. I just went through this ordeal back in April and converted to the RS single belt. No issues so far. Belt change is a snap!

J.O.

Now that it seems like the bearings and alternator feel good I agree and plan to install the belt and see if it works without any noise.

Yes I will be doing this myself. I have all the tools I need except I had to order the Snap-On Triple Square 10mm that everyone seemed to recommend over the Porsche tool. I had a 72 911 years ago so having one belt seems like the right way to go for me. But of course the 72 didn't have the A/C belt to deal with either.

TMc993

The "clattering" noise may have been the belt beginning to delaminate and flap about...Was the belt tension ever checked after the new belts were installed with the fan/alternator?

EMBPilot

sounds like the belt wasnt tensioned properly. when they are not set correctly the problem usually manifests in several weeks / months / miles later. The bearing starts to fail and the rest is history.

did the chatter sound like this?
this the sound of the fan machining itself to the fan housing... not good.

Just install RS set up and call it a day

JB 911

I agree with the others you most likely have a pretty straight forward diy ahead of you which will be a good bonding experience with your car. I would replace all three belts if I were you, they aren't that expensive then you'll have a baseline. (Or only 2 if you go the RS route)

Couple random thoughts:

1 if it was done at a Porsche dealership there may be some warranty on the work, or at least parts, no? Belts not a big deal, but it the alt shaft turns out to be bent...

2. Anybody else find it ironic that the original pulleys made it almost 20 years and the updated one the system puked a belt within a few months (I know I know nothing to do with the pulleys, all install technique or worn belt I'm sure, but found it ironic, just the same. For the record I'm on the original pulley holdout)

P-daddy

Good point Jamie. Most dealership work come with 12 mo/ 12k mile warranty. Give your Pcar dealership a call J.O.

J.O.

I agree. I will replace both belts, they all look bad to me. I live 1.5 hours from a dealership with a large but fun mountain pass in between, so taking it to the "local" dealer isn't too easy. I figure these parts will be far less than a tow truck over the pass. I will DIY the RS conversion and replace the belts. If it proves to be a problem with the alternator, etc. I will contact the local dealer and see about warranty.

J.O.

The sound was not that consistent or "clanggy". If I have read correctly and it is the bearing that won't matter if I go with the RS conversion. Is that correct?

P-daddy

Yea no more fan hub bearing with RS setup but improper tension will still damage alt bearing.