Fan & Housing In '85

[Discseven]

Just removed from my ’85.
___

Fan’s hub buldged one day…

Inside the hub and opposite the buldge.



Leading edges look normal. Trailing edges don't.

No time's wasted getting the alt out.


FAN HOUSING REMOVAL / INSTALLATION

Steps and tools needed are noted at the end of this post.


NEW FAN REFINISHING

A new Porsche fan. With some spare time on hand I'm going to polish and rebalance this thing.

“Skin” is quickly removed with a fine wire wheel. “Extra fine” would have been better --- this metal’s very soft. Cast seams between each blade are removed with a small flat file. To protect the center hub from abrasion, a mask is cut from thin sheet metal.



Dry sanding progresses through 150, 200, 400, 800 and 1200 grits.

I’m holding off on finishing the fan till after balancing it.
___

BALANCING

I mentally tested the idea of installing this fan without a balance and constantly envisioned it shaking itself and other parts to ruin. As a result, I’m now at the most sensible resource I’ve found locally (in Miami) for balancing. It’s TAW, a shop specializing in electrical motor works large and small.

The fan is first shafted then positioned on a floating wheel quadrangle. Seen from above, the drive belt is looped over the center of the shaft. To the right of the drive belt is a readable element taped to the shaft. A few inches away from the element (below it in the photo) is the optical sensor that scans the element’s motion. This sensor sends what it “sees” to a nearby computer for interpretation. After the test bed is set up, the fan’s weight and dimensions are entered into the computer and the test bed is completed and ready to roll.



7,000 rpm.

The attending technician, Hector, fine tunes the quadrangle’s geometry.

7,000 rpm turns out to be too fast for this equipment to interpret the fan’s imbalance. The fan’s too light and too small.

Fan speed is slowly reduced until the computer can produce an accurate reading. 3,200 rpm works. Slower than I planned but at this stage, there’s no good reason pack bags and leave.
___

The first reading presents on screen and the fan’s out of balance by 3.4 grams at 255 degrees. Whether these few grams would have meant disaster for associated parts… I don’t know.

A rapid weight loss program ensues… excess baggage accumulates on the track below.



Second reading. Notice the angle we’re now at now (17 degrees) compared to above (255). I would tease Hector for going overboard but choose silence to respect his maniacal concentration.

Air grinder is pulled out. Very fine grit.
___

The third reading displays and we’re half a gram out of balance at 18 degrees. I remember half a gram… it’s not much of anything.

Hector dives in once again with the grinder. After a few decisive blasts, he packs the grinder away and announces with no uncertainty and in a calm Latin accent, “Dats it. Wee done. One more spin… finished.” The fan is again spun up…



I’m not sure what Porsche’s fan balance specs are but eight one hundredths of a gram works for me. (In ounces = 0.0029).

Hector’s removed the shaft and approaches me with the fan cradled in his arm. Above at right, I just miss him pointing to the original well holes drilled by Porsche (or their fan supplier) … he’s telling me, “Whomever deed dis balancing, dey didn’t know what dey were doing.” (He doesn’t know this is a Porsche fan nor does he know of my tearing into it. The two already existing wells suggest a prior static balancing IMHO.)

This process took 1 hour at the shop and cost $80.
___

FINAL POLISHING & TOP COATING

The fan is now wet sanded with 800 then 1200. Then comes a cream polishing followed by a wheel buffing.

The fan has just been masked to receive one of four different top coatings that will be tested long term to see what coating will best preserve the finish. The exposed blades here will receive Armor All’s “Wheel Protectant.”



This stuff’s not like paint. It’s a drip-dry, hang-it-up-over-night program. When dry, the look and finish of this stuff is smooth and very-very thin.

Other blades were coated with:

1. Collonite No. 850 Metal Wax
2. MAAS Metal Polish
3. Flitz Corrosion Protection Polish

These coatings will remain untouched for a year or two to see how each performs. I’ll post again when results present something worth posting.

Fan’s done.


REJECTED TOP COATS

Sharkhide: The promotion for this stuff --- and word of mouth comments --- sound good but I decided to spare myself the lunar-excursion-expense for this product. I forgot exactly what it cost but it was tremendously unreasonable for the teaspoon of fluid that was needed.

Shelia Shine: In a nutshell… this stuff’s awful. Within four days of application, the blade with Shelia Shine applied to it had a 1.5 mm oxidation star chewing into the metal… while untreated blades looked great! I called the manufacturer. Their pleasant spokesperson expertly recited for me the marketing babble printed on the can’s label --- a meaningless endeavor since I had already bought into this useless product based on that babble!


NEW HOUSING

As far as I know, Vertex is the supplier (at the moment) of new 911 fan housings since Porsche has discontinued making them. List price: $589.



The setback for the crank pulley… quality control had the day off. I’m going to sort this out with a flat file and martini or two.


ALTERNATOR FIT

My alt fits nicely into the Vertex housing. Zero side play. Last few mm’s of insertion are tight enough so it’s necessary to pull the alt into its seat by its 3 nuts.


INSTALATION

My housingless 3.2.

Others who installed Vertex’s fan housings have commented on the top bolt holes not aligning with the holes in the cowling. I’m finding the same but this is an easy fix. Here’s the driver’s side. (The housing is pulled out from its final resting position to see where its holes are.)



Passenger’s side. Misalignment will be corrected after the housing is secured in its final resting place --- will grind cowling with a dremel.

Positioning the new housing is more easily done without the fan in the way. Once secured, the new fan with pulley and shims are dry fit to check the alignment between the crank and fan pulleys.
___

Pulley alignment is good. Fan’s removed for the shaft to get some anti seize. Shims are positioned so the new belt is intentionally too tight. New belts stretch to operating measure after just a few miles. By setting it too tight to start with, there’s no need to return to tighten it later.

The diameter of the ignition wires I run is smaller than stock wires so the wire retainers mounted atop the housing don’t secure them. To correct this, general use tubing is positioned to fill the gap between the retainer’s slots and the wires.



The finished assembly (awaiting the AC compressor.)

And… it works ~
___

FAN HOUSING REMOVAL / INSTALLATION

Only a few common hand tools are needed… the fan pulley’s locking tool, large socket for fan’s pulley nut, Allen wrench for the strap, small box and/or socket wrenches to remove the top bolts in the ignition wire retainers, the air deflector and wires to the alternator.

1. Hold fan still (with pulley locking wrench or some ingenuity) while pulley nut is removed.
2. Count shims on each side of the pulley and reinstall them as they were if using the same belt (and the tension was correct.) All shims must go back one way or another --- in front or behind the front pulley half.
3. Undo ignition wire retainers located atop the housing.
4. Undo Allen bolt securing strap around housing.
5. Position the housing to access the three nuts securing the air deflector to the housing. Nuts are located behind the housing. How much the housing can be pulled out from under the cowling depends on the length of the wires attached to the alternator. There are a total of 6 nuts of the same size located behind the housing. Undoing all 6 does not hurt but the 3 that secure the deflector to the housing MUST be removed to proceed further. (Look at the housing photo above to see where the nut locations are based on the bolt holes in the housing.)
6. Once the air deflector is free, push it towards the front of the car and detach the wires on the alternator noting which wire(s) go where.
7. Housing (including fan and alternator) can now come out.
8. After housing comes out, the air deflector slips out over the wires that run through it and it comes out.
9. With the housing out, it’s a good time to check for toasted critters and other objects that may be obstructing airflow over the cylinders. Also inspect the duct positioned over #6 cylinder for clear passage to the oil radiator located behind #6. Cleaning terminals and checking connection bolt/nut tightness is also a good idea at this stage.

• Install in reverse sequence.