Quote:
Originally Posted by ddweave
Before doing anything major, be sure to try running the engine without the fan belt to rule out the fan being out of balance.
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Good point on the fan being out of balance...
This past spring a car with an engine I rebuilt showed up at my shop to help find a source of a severe vibration. Before delivery of the engine, I ran the engine on my break-in stand over 3 hours and had not noted any vibration. I had my waterpump and fan on for the break-in.
The observed vibration was ever present but most noticeable at higher RPM and upon quick let off of the gas pedal. Suspecting the fan, it was removed and checked. The cast aluminum fan was way out of balance. Replacing the fan with a balanced one solved the problem.
Tom Wessenberg and Brent Terry have posted info on the device used to balance fans. Search their posts for more info.
The source of vibration in this thread may well be something else but checking the fan is so little work....
Good Day!
Dave in MN