Engine

Cooling Fan Clutch Rehab

The 928 (up thru MY86) uses a thermostatically-controlled silicone fluid cooling fan clutch. By
failing to move enough air through the radiator, this clutch may well be responsible for many of
the high-temperature problems that we experience. Since a replacement clutch lists for about
$400 and sells for about $300, not many of us will replace it on suspicion alone, and there isn't a
test that tell us whether it is slipping due to a loss of silicone fluid.

There is, however, a repair procedure for the clutch. This procedure is not Porsche-approved,
and will not guarantee original performance of the clutch, but it will greatly improve the
performance of a faulty clutch. I would expect this to take you one or two hours to complete.
Try the procedure at your own risk. I don't know of any way that this could damage your car,
but if you find a way to do so, don't blame me! YMMV!

1. Toyota uses a similar fan clutch, but they also sell silicone fluid to refill their clutches. Go to
your Toyota dealer, and buy two bottles of this silicone oil, at a cost of $6 or $7 for a very small
bottle. You will also eed a small quantity of silicone sealer (RTV), and a heat source. The best is
a flameless hot air gun, but you might be able to use a propane torch if you are VERY careful.

2. Remove your cooling fan, complete with fan, clutch, bracket and pulley. No disassembly of
the fan unit is required except as detailed in Steps 4 and 5.

3. Carefully clean the fan unit, especially the front face of the clutch, which faces the radiator.
Clamp the fan bracket to a work surface with the fan face-up in a horizontal position, leaving the
fan free to rotate.

4. There should be a 1" x 3" piece of sheet metal across the center of the clutch. This is a
bimetallic element. DON'T BEND IT! The strip is retained by slots cut into the ribs on the fan,
and is kept from rotating out of the slots by small dabs of silicone sealer (RTV). Remove the
RTV, and CAREFULLY slide the strip slightly to free it from the ribs. Remember which side is
up.

5. Under the strip should be a silicone rubber grommet, with a small metal rod in the center of
the grommet. Remove the rod, being careful to not lose it. Remove the grommet, being careful
not to tear it. Cut the tip off the bottle of silicone oil at the very end.

6. Heat the fan clutch while rotating the fan and clutch at a moderate speed. (Be careful not to
overheat and damage the fan.) This expands the air in the clutch, and moves the oil in the clutch
to the outer edges.

7. Remove the heat source. Continue to rotate the fan and clutch, and drip the oil into the
grommet hole. The combination of cooling and rotation will pull the oil in and distribute it to the
outer edges. When oil stops going into the hole, repeat the cycle of heating and cooling. I
suggest using two bottles, since there is no way of knowing how much oil is really needed.

8. Replace the grommet, and insert the metal rod. Carefully replace the metal strip, being certain
to not bend it, and to get the right side up. Apply small dabs of RTV to keep it from moving.

9. Reinstall the fan unit. Let me know whether or not the procedure helped your overheating
problems.

Wally Plumley
928 Specialists