deadhead1960

Looking for some guidance/suggestions regarding my [new to me] 993 with 16k miles. After driving the car problem free for 250 miles last week the dashboard lit up like a christmas tree. A quick diagnosis led to the replacement of the alternator with a Bosch rebuilt unit. At the time the belt did not break and was not replaced (tech said it was fine). After driving the car for 20 miles afterwards the same dashboard lights illuminated along with a burning smell. A quick look in the engine bay revealed a broken and scorched alternator belt. The belt is being replaced today. Any other precautions or issues to address? I am using an OEM belt. Will the belt stretch and have to be re-tensioned? Should the shop charge me for installing this belt or should he have changed the belt when he replaced the alternator, to establish a new baseline? I have also heard the bearing in the fan could seize and that could cause the alternator belt to break; is it possible both the alternator and this bearing to go bad within days of each other. Lastly, for what it's worth, I'm not using my regular independent due to the distance, so my comfortable level with the current shop is not super high. Thoughts?

ilko

Jay, it is unlikely that the bearing failed IMO. Sounds more like the belt wasn't properly tensioned after the install of the new alternator. There are shims on the hub that are added/removed during install for proper tension. The new alternator may have required more or fewer shims than the old one in order to get the belt tensioned to the correct spec. A qualified mechanic would use a gauge to check the belt tension prior to buttoning everything up.

Quadcammer

Jay,
A lot of this depends on how much you trust this indy. If he knows what he's doing, he would check to see how the bearing looks/sounds, would make sure the reman alternator spins easily (it should as a seized alternator would cause problems for both belts as I recall), and would check tension on the belts.

Also, make sure that your Indy is using only the PORSCHE branded belts. There have been questions raised about aftermarket belts in terms of thickness, quality, and even possible misfires.

My bet, with a correctly tensioned OEM branded belt, you will be good to go.

Nevertheless, I will bring some tools with me on saturday so that we can change the belt if its necessary for whatever reason.

Coop

I had this very issue. A few times. Even broke a belt on the highway and had to navigate without power accross four lanes. My indy changed the pulley to a 993 turbo pulley and have never looked back. Stil using the OEM Porsche belt. This could be the cause...

deadhead1960

All great feedback...thanks. I will purchase another OEM belt...just in case and carry it with me. This shop did not use a gauge to check the tension. If I have no other issues I will still bring it to my regular shop next week after Saturday's long drive and have them re-check the tension as I understand the belt could stretch a bit. Thanks again!

IXLR8

I can see an alternator belt breaking, but scorched means the belt was overheating and you did mention "burning smell".


Visually check to see that the pulleys align as they should.


Maybe I misunderstood, but you can't change a belt yourself? Maybe have QC show you...its easy and handy should it happen on the road.

Quadcammer

Jay,
do you have the updated alternator pulley?

Can you snap a pic of the alternator pulley?

ilko

We can do this on Saturday in a parking lot. I carry a 24mm wrench in my car for that purpose alone.

deadhead1960

Umm...where is it located and how does it differ from the original. Remember, car is new to me...so no clue as to whether it's been updated.

Ilko...thanks for the offer. Let's see how it plays out. Weather permitting I want to drive the car locally 40-50 miles over the next few days to make sure there are no other issues. I'll have an extra belt just in case.

Quadcammer

Its located in the center of the fan...closest pulley to the rear of the car.

If you snap an upclose pic of that area I can tell you.

Easiest way is whether or not you see a separate washer behind the big nut.

deadhead1960

Here ya go...I see the washer!

Quadcammer

yup thats the old one. May want to inquire at local dealers on the new one.

IXLR8

The new style alternator pulley. Pulley shims should now stored in a zip-lock bag in your tool kit.

mjsporsche

I am impressed with all the knowledge on this forum. Jay - drive to your regular indy and get it done right.

Mark

Mike J

** wrote this this morning and you guys responded while it was sitting there - forgot to hit the submit button. Nice job, great help on this site!!

The belts typically last a while, but there was a pulley update that came out a while ago that may help if the problem persists.

You should carry spare belts and be able to change them in case this happens while out in the countryside. Most people carry belts, confirmed tools to change the belt (the tool kit is usually lacking a spine wrench to hold the shaft still, and the 24mm wrench for taking off the main nut), a quart of oil, clean rags, etc.

The belts will stretch a bit, but not usually so much they require an adjustment. There are no tensioners, the system uses shims on the pulley to adjusted the required belt length. If the alternator bearing was going bad, that could cause a lot of load on the belt and cause long term fatigue and breakage. It may also be that the tech did not have enough tension on the belt, and after the installation it was slipping and eventually failed. Hard to tell.

Cheers,

Mike