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Q: Can't Figure Out Engine Noise

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Hi there! For the past 6-8 months, I've noticed that my car sounds like it's working really hard to do the things it used to do with ease. I have no difficulty or delay in starting the vehicle, but once it's on, there's a loud, low-pitched roar/grumble/growl type of sound, coming from the alternator area under the hood. It happens when I start the car, the car is idling, and especially when I am accelerating. No noise on braking, turning, or coasting. There is no vibration or funny smells. I drive this car about 150 miles every day, to and from school. I have had transmission fluid & filter replacement and flush recently, I use fuel injector cleaner every 3,000 miles, I have the oil changed every 2 months exactly, my battery appears to be in good shape, I just got new tires, and I've never been in a collision in this car. Shocks and struts have been replaced before so they shouldn't be worn, water pump was replaced recently, and all fluid levels are maintained carefully. I'm lost!

My car has 112000 miles.
My car has an automatic transmission.

A: Typically, I would perform an initial diagn...

Typically, I would perform an initial diagnosis by disconnecting the serpentine belt and operating the engine for a minute. That belt drives a lot of devices that can make a lot of noise and thus a whole collection of possibilities can be dealt with quickly in one fell swoop. If by chance the noise does go away by eliminating all belt-driven devices, then you know the noise is from a belt driven accessory or pulley and it’s easy to trace from there. If the noise remains, the I would have a certified technician, such as one from YourMechanic, diagnose the noise in person so that this can be addressed appropriately.

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