autobonrun

Maybe this is just an early 911 thing, but I'm wondering if anyone has tried polishing or powdercoating the fan on their 993? I'm also curious if the 993 fan is made of magnesium like the earlier cars?

The downside of polishing is that the patina returns somewhat after about 6 months, but on my earlier SC, anytime I change the fan belt, I repolish the fan. It takes about an hour after the first time. Some have powdercoated their fan so they don't go through the polishing exercise but I like the polished look better.

http://forums.pelicanparts.com/showt...0&pagenumber=1

Joe S.

I've seen several 993's with the fan housing and fan painted. Looked good. Anything would look better than the stock color. Beige???

Porscheologist

I recently had the motor out and had a close look at the fan. Boy is it ugly. Beige of all colors. I powder coated (red) the fan on my SC but after a year the edges of the fan began to chip. I would hesistate to do it again. It was a ton of work to get it out. Magnesium is a real pain as its very fragil. You drop that fan you will break it. Bu then again maybe on a 993 its aluminum???

Peter S 993tt

No - I think it's still magnesium, but I think the shroud is aluminum.

Leland Pate

An even better question would be why the TT's got the old flat style fans while the NA cars got the swept blade fans. I've been told the TT's got the old style fans because they move more air and combat the heat issues better. But, if that's the case, why the H.E Double Hockey Sticks did Porsche develop a fan that was not as efficient as the one it replaced.

And on another related note, I just bought a 993 fan off eBay for $9.00. It should get here in a few days. I am going to make something decorative out of it and may polish it. This one has a crack at the base of one of the blades, hence the dirt cheap price.

tj90

I actually think both are aluminum. I painted my shroud with dark dray engine paint and polished my fan to be as close to mirror finish as possible - 8 hours on and off with a dremel and buffing compound.. The mirror finish will dull over time but the OEM paint on mine was chipping.

Also, a powder coater did not want to touch my fan cause he was concerned about the clearances in the housing, blasting deformation and balance. I dont know if he was being too conservative since Ive seen powder coated fans before...

mr_bock

When I had my SC installed, the shop sent the fan and shroud out for painting. The paint shop took extra care as to not get too much paint on the fan tips. The fan to shroud clearence is very tight and there will be some rub areas. This is espically true if the alternator bearing has some radial play. Having the fan painted to match the body color looks great!!!! They painted the shroud a golden color to match the yellow iridite finish on the aluminum SC parts. There might be a corrosion issue with the buffed magnesium or aluminum unless coated. Just my $0.02.

troutrover

That red looks very good. Hmmm?

autobonrun

Thanks for the pictures. I think at the first opportunity, I'll powdercoat the housing and polish the fan similar to the way I've done my SC. Since my 993 is guards red, red should make for a nice engine accent. I too dislike the beige fan color and will probably get around to changing it.

After polishing the fan, corrosion is not an issue but if painted, the clearance does need to be checked. Most just make sure not to paint the fan edges or they remove the paint from the edges after painting. Also, I keep the paint off the pulley portion where the belt contacts. It's fairly easy to tape off the center part. Here's my 79SC after powdercoating and polishing. I still would like to find out for certain if the 993 fan is magnesium or aluminum. Seems to be conflicting opinions on that.

Leland Pate

Are there any simple tests we can perform on the fan to determine whether it is mag. or aluminum?

planeguy67

Light one corner with a welding torch. If the entire fan ignites into a brilliant white flame leaving nothing but a small pile of ash afterwards, then it's magnesium. If the corner just wrinkles and melts, it's aluminum.

Seriously, I can't think of anything that won't damage the fan somehow by testing it except dunking it in water and measuring its density (Mg is lighter than Al). I also know magnesium will tarnish far more rapidly than aluminum will because it is so reactive, but sanding a small patch on your fan and waiting for it to crud over may be inconclusive.

Then again, magnesium is a very common metal in aluminum alloys, so the fan may be BOTH!!!

brucec59

Is there a coating on the stock fan? Should it not be polished or buffed?

FisterD

How about polish it, and then "clear" powdercoat it.

Leland Pate

Ah yes... Mark Hargett's twin turbo 3.0.

You guys shoulda seen that motor when he started.

autobonrun

FisterD, that is one beautiful engine.

I tried to research the issue of polishing magnesium a while back and actually sent the question to a magnesium supplier. I was put in contact with one of their engineers and received this email response.

" The short answer to your inquiry is that there is nothing I know that will give you that “polished look” on magnesium for the long term. This is the same issue people have for polished magnesium wheels. If you “polish” magnesium and simply apply a clear coat, the clear coat will delaminate (turn milky) from the magnesium at sharp edges and stone damage sites in even quite mild (humid/wet) conditions. This is because of the following factors –

1) Polishing with certain abrasives can contaminate a magnesium surface with cathodic (iron containing) impurities. This has the effect of further increasing the corrosion rate of magnesium alloys and aggravates the situation. Safe polishing media for magnesium would be high purity aluminum oxide, silicon carbide, glass or diamond. Do not use emery powder. Never use a wire brush to “clean” magnesium components.

2) Magnesium is an alkali metal and requires a conversion coating to be applied before painting. The conversion coating will passivate the magnesium surface and improve paint adhesion. This will slow or prevent delamination of the paint under corrosive conditions. All the best conversion coatings for magnesium are colored and most contain chromates. The “best” available conversion coating that would maintain a “shiny” finish is known as the # 21 Chemical Treatment (If you send me a fax number I can copy you with the chemical formulation which does contain hexavalent chrome compounds).

3) Magnesium is an alkali metal and epoxy based paints are preferred. Epoxy based paints suffer from UV degradation so should not be used as a top coat. Its probable best to apply a clear epoxy primer followed by a clear polyurethane for the look you are after. Cellulose paints on magnesium behave poorly.

Don’t know if this will help you – why not chromate the fan assembly using one of the better chromate treatments, rinse, dry the chromate film between 110 to 120 C, then apply a silver base/clear coat system."

As you can see, magnesium is a difficult metal to work with. Others have pointed out the fire hazard associated with magnesium. This fact makes several shops hesitant to work with the material near an oven. The fact that the earlier fans are not entirely magnesium (the center hub for the belt is steel) makes the process all the more complicated. For these reasons, I have chosen just to hand polish mine on an infrequent basis.

It seems many have had success with painting them but my concern for clearance and the issues mentioned in the attached email are why I haven't gone that route. Before going either route on the 993 fan, it's important to determine the metallurgy and the type coating used by the factory. The magnetic test does not work for determining metallurgy, as both aluminum and magnesium are non-magnetic; at least I know for certain magnesium is and I seem to recall aluminum is as well. I'll keep searching for an answer as well.

I recommend that anyone thinking of removing the factory coating from a 993 fan should do their research first as well. I know there are little things on the earlier cars that can save lots of headaches; For example don't paint the back portion of the housing where the alternator fits as it's already extremely tight. Many also recommend not painting the fan tips. Again, I'm just coming up to speed on the 993 setup and these things may not be an issue. Just check first.