Alternator fan/Woodruf key sheared?

rlane · 10-05-2005, 05:05 PM

I pulled the alternator on my 78SC last night due to really disturbing metallic noises coming from there on start up the last month or so. After cursing those shroud/extension nuts I pulled it out and off slides the fan! Not a tight fit or an issue at all. The woodruf key is no where to be seen!. Looking at the backside of the fan there is clearly mettalic damage to the high spots there. I am geussing the key sheared and did this? Or perhaps I pushed the key back when I installed last time.
Has anybody seen this?
What size is the woodruf key, or a Porche part number?

afterburn 549 · 10-05-2005, 05:15 PM

you have to be real carefull on install as the key just luvs to slide on back and out.....well thats my exp.

David · David's Garage

I'd get a Porsche one to be safe. Did the bearing go and then the key sheared?

rlane · 10-05-2005, 05:27 PM

No...the alt spins freely and until I was pulling in to my garage the alt light had not even lit up. I dropped the alt off at a reputable shop to have it checked out, I looked at the visible bearings (rear as mounted in the assembly) and they looked OK...but I am not at all sure there are not lots of metal bits just waiting to cause issues....
David...do you happen to know the Porsche part #?

TerryH · TerryH's Garage

Alt shop should have a million keys laying around. I would scrutinize the fan bore for roundness and the alt shaft for wear. Without the key there is the possibility the fan could have spun on the shaft.

If they key actually sheared, the remainder would still be in the keyway on the alt shaft.

David · David's Garage

I checked the PET for the key and it's not there. Therefor I assume it's a standard size that you don't need to go to Porsche for.

rlane · 10-06-2005, 05:43 AM

I'll check with the alternator shop, I cleaned up the fan last night and will run it by today so they can asemble and test. The keyway had no pieces visible, I even went back and checked out the garage floor and that yawning space down by the crank pulley that seems to attract all small parts!

rlane · 10-06-2005, 04:49 PM

anybody else ever seen this?

TerryH · TerryH's Garage

Was wondering how long the alternator had been in the car? It is possible the key wasn't there since the last repair and it took this long for it to become evident. Also the chance the key fell and bounced out of sight when the fan came off. But, the fact that the fan was loose, leads me to believe there may be some wear between the shaft and fan from the lack of a key.

The genius behind the woodruff key is that it cannot walk out of the keyway once it is properly captured by the component. However, it can easily be displaced during assembly if care is not taken.

TWork · 10-07-2005, 09:50 AM

Having pulled my fan off 3-4 times in the last month to replace an alternator, then to replace a bad rebuilt alternator, etc., I think its pretty tough to sheer a woodruf key. More likely, it fell out when you were pulling the fan out of the shroud. Once you break the fan free, it falls out pretty easily. I've had that happen numerous times. As for getting the "right" key, if you do a search in the PP parts catalog for "woodruf" it should come up pretty easily.

T.

rlane · 10-09-2005, 05:32 AM

I reinstalled the alternator yesterday, that woodruf key is a real pain. It must have taken 50 tries to get everything lined up just right so the key would slide up in to the groove in the fan. Jst keeps wanting to slip out. Has anybody ever used a light coat of glue to keep the key seated in the alt shaft?

4to8m8 · 4to8m8's Garage

Go to Home Depot and buy a handfull for a dollar. One of them will fit. I used one of my daughter's booger's to keep the woodruf key in place!

Gunter · Gunter's Garage

On any key, you need to fit it first into both sides. Try the woodruf key first with the flat side in the fan-keyway. Sometimes it needs to be filed a little to make sure it is snug but still slides. Then try the key in the shaft. If it is too loose in the shaft, a slight tap on the keyway with a hammer will narrow the hole. Use a little antiseize when installing.
Your woodruf key is somewhere; it didn't shear off. The belt would slip before the key breaks.

rlane · 10-09-2005, 08:54 AM

I did file the key a tiny bit..used a tiny bit of the dielectric grease I had out for reconnecting the alt wires...almost as good as buggers....
I agree that the key didn't shear, as Twork said it clearly (in retrospect!) came loose as I adjusted the pulley last month, then was loose inside the back of the fan, it amazes me that the pulley still didn't rotate on the alt shaft thru a 1100 mile trip to Virginia and back! I am so glad to have luck..sure I sure don't have skill...