944S2 Alternator Belt

[Billyblue360]

This winter I purchased a 1990 944s2 cabrio. I had it stored in my garage all winter and just got it out a couple weeks ago. I noticed last weekend that it was making a rattling noise that was particularly noticeable at idle. When I checked under the hood It seemed to be coming from the alternator so I thought it was an alternator bearing. I toOK the belt off to inspect the alternator and their was a little bit of play in the alternator bearing so I had it rebuilt. I put the rebuilt alternator in the car today tensioned the belt and start her up and the car seemed to run OK. I toOK the car for a quick spin to the corner store and by the time I got there the car was rattling really bad. On my way back the alternator stopped charging. When I got home I toOK it apart again and noticed that the pulley on the crankshaft was loose. I could shake it around with my hand and it had about 1/2" of play. I'm guessing that the problem is with the pulley. Any ideas on how I can troubleshoot the problem and what it takes to repair the pulley?

[Billyblue360]

My guess is that the bolts holding on the pulley have come loose. Anyone know whats involved with getting in there to check and what size pan head screw i'd need?

[Makis]

I have got that on my S2 too and the problem was that the pulley is only hold down by 4 bolts. The torque the engine puts on the alternator had actually shred the bolts in my car. I had it fixed twice but it happened again. In the end I have to get a new pulley for the balance shaft which the alternatator pulley bolts on. On the updated version of the pulley, Porsche now uses 8 bolts. The problem seems now solved. You may have to go this way. It must be a common problem if the updated balance shaft pulley now required 8 bolts.

[Billyblue360]

Thanks Makis,

Does the existing balance gear have 8 holes or am I going to need a need a new balance gear too? Would I be able to just drill out 4 additional holes in my pulley?
Are the bolts to bolt on the pulley M6 pan head screws? Do you know what length they are?

[944 Ecology]

The alternator drive pulley on the crankshaft is the dreaded two piece, i.e. two metal pieces with connecting vulcanized rubber in between the two. Your rubber piece may have disintegrated to the point where it is slipping and making noise.

[Makis]

Originally Posted by Billyblue360

Thanks Makis,

Does the existing balance gear have 8 holes or am I going to need a need a new balance gear too? Would I be able to just drill out 4 additional holes in my pulley?
Are the bolts to bolt on the pulley M6 pan head screws? Do you know what length they are?

The existing balance gear (on my 1991 S2) had 4 holes only and not possible to have 4 more. I purchased a new one from porsche (944 102 209 11) and it came with 8 holes. It may have an upgraded part number as they were not doing the 4 hole one any more.
The screws are (900 067 279 08) according to my pdf part list, but they not mention size. The main alternator pulley has holes to accommodate the additional 4 bolts. The bolts can't be too long or too short so you will have to get the correct size.

[Shifter]

I had a similar issue on my S2, but my problem was the crank bolt was backing out and letting the pulley wobble. I got lucky and caught it before I lost the timing belt. Just another think to check while you are in there.