It’s the unmistakable centre piece of an Air Cooled 911, the Alternator / Cooling Fan. Propelled by a Belt off the Lower Pulley, it draws air in through its blades over the engine block, providing much needed cooling. Despite the assertion that the 911 Air Cooled engine is just that, it is actually Oil Cooled. Hot oil is pumped from the Engine to the front of the car via pipes under the sills, to two radiator[s] [behind the intake scoops / grill] at the front of the car for cooling. For more performance oriented 911s, an additional third Oil Radiator can be installed to further assist in this endeavour to good effect.
But I digress.. The Fan.. This one..
Nice isn’t it, well it should be, this is the one in my 993 after its refurbishment, following the Alternator Bearing fail which made a horrible noise. In all honesty, it had been making a tolerable noise for some time [shame on me] I just didn’t know that it was a sign of bad things to come.
The Engine would made a sort of whistle/whine when up to speed and warm, and always reminded me of a chord in the Thin White Duke mix of Starsailor’s Four To The Floor [listen from 4:32 to about 4:46]. I can now say that that noise was a sign that things were about to get worse. I know this, because they did, albeit much later. And as it turns out, when I was approximately 50 Miles from Home in Portsmouth for the Weekend, primarily to meet and listen to Rod Emory at the Porsche Centre.
The morning after the Friday evening event, driving to friends in Southsea, a grumbling moaning noise emanating from the back of the 993 started. I pulled over as soon as was convenient, popped the Engine Lid and listened. Didn’t sound good. I thought it was the Lower Pulley Bearing, but as it turned out, and fortunately, it was the Alternator Fan Bearing.
The following morning, I called the AA and they duly arrived within the hour [!] to chauffeur the 993, Hollie and I back to Brighton. Sure, I could have probably driven/nursed the 993 back to Brighton without incident, but really, what use is having an AA Membership if you’re not going to use it.
Dropped off at my local Garage, Andy whipped the Alternator Fan and Shroud assembly out; I order the new Bearing, £100, install. Simples.
Not. So. Simples.
That Fan spins at quite a speed, and because there is no filter as such, any airborne dirt, dust and detritus is drawn directly onto those Magnesium Vanes potentially [and actually] pitting and damaging the painted surface. The same can be said of the Shroud that houses the Fan, also made of Magnesium.
So a refurbishment is a good idea before things get so pitted that the parts become corroded and the tolerance between the two increases permitting air around the edge rather than being forced through the Vanes and accelerated in the process. So, off to Tactical Coatings UK who, after a bit of Googling, offer a specialised finish called Cerakote for Magnesium that is effective at heat resistance and dissipation; perfect for engine bay applications.
I went for a Dark Midnight Bronze on the Shroud, and the result is/was fantastic. A sublime, almost retro finish that wouldn’t look out of place in a highly modified Flat Six; the team at Tactical Coatings were great. Shroud done. Media Blast, Cerakote, £100, install. Simples.
Next the Fan and for this I wanted a lighter Bronze to contrast but compliment the Shroud; Burnt Bronze. Media Blast, Cerakote, £100, install. Simples.
Not. So. Simples.
Turns out that my Magnesium Alternator Fan had simply had enough, and after 25 Years of Service, threw the towel in. Magnesium is not reparable by welding, so a new Fan it was. Something in the region of £450.
These. Things. Happen. Besides, I’m sure I can find a Panel Beater [or Pub] that will smooth out [or forget] the Dent that my Wallet took on that one. All reassembled, and spinning smoothly and silently. No Whistle.
For interests sake, the broken Fan has been recycled as a Wall Clock; 12 Vanes, 12 Hours. Perfecto.