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"Whirr" sound coming from under the hood

3K views 2 replies 3 participants last post by  speedup 
#1 ·
took a little shopping trip this weekend and all was fine on the way to the store. when we got in the car to head home I noticed a sound coming from under the hood. Hard to describe the sound, kinda sounds like a baseball card against a bike spoke. I immediately thought the fan was off balance but after inspecting it all is fine except a small chip taken out of one of the blades. I thought that was throwing off the balance but the fan appears to run fine and balanced with the engine running. Anyone have any ideas what could be causing this? It's running fine (no power loss, no overheating, no funny smells) other than the sound...ugh that sound!
 
#2 ·
So this is happening when idling/revving - i.e. not the drivetrain?

I'd suspect the fan also, it's possible the noise is coming from the fan clutch, not the blades. Also could be a failing water pump, check for leaks where it attaches behind the fan. That would eventually make the fan wobble also. But I'd also strongly suspect the alternator - unless you are still using ac where you are this time of year? then possibly the compressor- but you'd probably have figured that out!

I hold a length of wood or metal against each component to test, and often the vibration makes it obvious where the noise is coming from..
 
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