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The 2013 revamp of the desktop Mac series known as the Mac Pro.

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2-3 second grinding noise on startup

There’s a short (2-3 second) grinding noise at the beginning of startup, before anything appears on the screen. I’ve taken the cover off and the fan is rotating ok. Any idea what it might be? It works ok, just worrisome.

Update (03/14/2020)

I replaced the fan. It doesn’t work. I think I may have damaged one of the electrical ribbons, going to see if shop can fix. But also, still have the grinding noise. Video attached.

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Has to be the fan.

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A grinding noise implies physical movement, and as the only moving part inside the Mac Pro is the fan that kind of narrows the possibilities.

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I know, but the fan spins freely no noise, after shut down and opening the can. What initiates the fan movement on startup?

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The fan is little more than a self-cooling electric motor. I would guess that the fan is either slightly off-balance or the bearings are slightly worn, and at startup (low RPM — but faster than you can spin by hand) it wobbles enough to make noise. Once it gets up to speed it stabilizes enough that it stops making noise. If this is correct, your fan will get gradually worse until it fails completely.

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Thanks. Makes sense. Find a new fan and do this: Mac Pro Late 2013 Fan Replacement. Some of the comments under this sound familar.

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There is a non-moving part that can make a noise.

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John Cathey crwdns2934231:0crwdne2934231:0
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