The C/GT was back on it's feet for several days before the weather was
nice enough to fire it up and see if the crank pulley was going to go
along with the rest of the motor. Last night there was a Club event so I
snuck out of work a little early to go through the final preflight
checklist so I could attend in my favorite LBC.
I believe I have finally made a definitive determination of what may
have caused the crank pulley to loosen and also resulted in the play
where the woodruff key indexes the pulley to the crank. After careful
and thoughtful analysis, I believe the water pump fan became unbalanced.
This happened over time and would explain a bit of high-end vibration
that has become worse the last few outings. As the water pump spins on
the outside of the crank pulley (i.e., will require the dampner to damp
both the engine pulses and the the water pump shaft pulses, this
eventually overtaxed the woodruff key and mounting system for the crank
pulley.
To assist the less skilled troubleshooter, I would like to pass along my
diagnostic process. As background, the fan on the C/GT is a yellow,
plastic flex fan. Although it looks like it comes from an LBC, all the
other 'C's I have seen use (noisy, heavy) metal blades. Anyway, I
believe this flex fan was the culprit.
The Troubleshooting Process:
Within 15 minutes of having the car fired up again, and while briskly
going through the gears merging onto an expressway, several of the fan
blades tired of flying in formation. The immediate results were a very
loud commotion under the bonnet; the almost instantaneous presence of
great clouds of steamed antifreeze; and a great amount of rumbling and
general unrest from the remaining fan blades still willing to soldier
on.
Sigh.
Bob Allen, Kansas City, '69CGT on a tow chain, a smug '75TR6
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