chris walrod

760mm is the belt length if you need to get a belt locally just to get you home. Then, replace with OEM belts only.

johzev

When I first acquired my car I was getting a code for miss fire. The problem was corrected by removing the after market belts and replacing them with oem belts. The aftermarket belt on my car was the correct length but the shape was a little different than oem which caused it to slip.

Definitely would stay away from aftermarket belts because of this experience.

TheOtherEric

Correct me if I'm wrong, but doesn't that issue pertain only to the fan belt? I thought it was ok to deviate with the alternator belt. Maybe i have it backwards.

cabrio993

The problem is with the width of the non-OEM alternator belts. Even though the length may be the same, the width of the non-OEM belts don't let them sit down all the way into the pulley. The alternator then skips and the ODB sensor detects this skip as a misfire triggering a CEL.

Here is my post about it from a year go:
https://rennlist.com/forums/993-foru...hlight=misfire

chris walrod

since the alternator has more inertia than the fan, I would think the alt belt would be that much more sensitive to causing misfires. Just a thought.

black ice

Actually it's the other way around - the factory belts are something like 1-1.5mm wider than the off-the-shelf belt from pep boys. If you find you have non-factory belts in your car and you go back to factory, you have to make sure you have enough shims because the belts will ride much higher and therefore will be tighter.

Also important to know exactly what size belts your car needs for when the Porsche store is closed and you don't have a backup. IIRC, on my 95 without the pulley update I need 760mm on the alt and 776mm on the fan but the non-porsche parts place may give you something close or something wrong altogether. I think on 95s with the pulley update the belt length for the alt went to 757mm.

dave

cabrio993

In my case, the 2 Contis that caused the problem were .5mm wider than OEM.

Porsche belt Part number 999 192 343 50 has dimensions 9.5x760mm, the Conti that was on the car with same refernec number was 10x760mm ( .5mm wider)

Porsche belt Part number 999 192 338 50 has dimesions 9.5x766mm, the Conti that was on the car was 10x765mm ( .5mm wider & 1 mm shorter)

I tried changing the shims, but that didn't help either, being the same lenght as OEM, it would just change the profile of the cross section of the belt, but it would still pinch it. However, If the belt would have been narrower than OEM as you say, the problem would not have been as bad as the belt would just have gone deeper into the pulley.

Going to OEM belts was what fixed it for me.

Dan in Florida

I'll second the recommendation to use only OEM Porsche belts. (Ask me why). And carry an extra set in your car - they won't be easy to find on the road.

Dan

Avenger6

I actually made it over 200 miles (on highway) with no alternator after a belt breakage. (I had been working on things up front and I had taken out the spare belts and forgot them at home DOH!)

Just turn everything off (A/C especially) and you'll make it eight miles just fine.

cabrio993

Wow...What kind of battery did you have there? Are you sure it was the alternator belt and not the fan belt?

I had mine break a few years ago, all lights when crazy on the dash, I continued maybe 1-2 more miles and the car finally died. Couldn't crank it up anymore as the battery was drained. MAybe my battery was weak to start with.

From that time, I always carry spare belts in the car.

Avenger6

Errr.... yes, it was the alternator belt. I wouldn't have driven it without the fan.

I just shut EVERYTHING off, didn't use any lights (it was daylight), and basically played Apollo 13.... used NO extra electrical power of any kind... and OK, since battery life in this case was a function of load over time, not distance, and I was on the Autobahn in a lightly traveled area where I could run at a pretty steady 120mph, I was able to cover 200-210 miles before it gave out. The car died coming into driveway, and didn't have enough juice to start again.

ZombiePorsche44

Correct me if I'm mistaken but I was under the assumption that the inner of the two belts on the fan was the alternator belt and the outer was the fan belt.

and I totally agree about never installing aftermarket belts, the difference in price vs an OEM belt is insignificant when compared to the possible problems non oem might cause.

ZP44

b5audia4

So my alternator belt just self destructed, luckily I made it home - sitting in the middle of the driveway now.

I want to try to tackle this, but do I need this special Porsche "12 point allen tool part#999 571 052 02"? I have read the threads, but still a bit confused (I am still learning a lot of these 993 DIYs).

Many thanks!

AOW162435

Joe,
You'll need a 10mm "triple-square" (or "XZN") to hold the alternator shaft. No other way to crack the main nut.


Andreas

b5audia4

Thanks Andreas. I hope I can find this at a local auto-hardware store.

Also, how can I tell if I have an updated pulley or not? Based on the VIN per P-car.com and looking at the past service history, it doesn't appear to have been updated. This was a TSB and not a recall right?

Thanks guys!