2016 Hyundai Accent SE 1.6L 4cyl with 72,000 miles. 5 days ago, I removed the old battery to exchange it as it was dead, and didn’t get back to installing the new one until two days ago, so the battery terminals were unhooked for three days. The battery works fine currently, but I’ve noticed that there is now a whirring/humming when the car is accelerating around 1500 RMPs. The sound only occurs then, so I haven’t been able to replicate it in park, since it only occurs when driving. It does not occur in neutral (when on the highway or in the driveway). It sounds like a tricked-out exhaust/muffler that a teenage boy would have on his truck or honda civic. Since it only occurs at a very specific RPM, I’m at a loss as to what it could be, since I don’t believe it is battery related as the battery/terminals are clean, new, appropriate and installed. Any help and direction is appreciated!
Alternators can make a noise usually described as “whining” if the battery needs a lot of charging, so that’s one possibility. Another, disconnecting the battery will reset all the computers, which means they have to re-learn the engine operating parameters. So that might be the cause. If either of those is the cause just normal driving for a couple weeks should solve it. Still good idea to check the engine and transmission fluid levels. Differential and transmission gears can make this sort of noise too, so that’s something to consider if it gets worse.
Drive the vehicle a little longer to see if the noise goes away, and cross your fingers.
https://www.aa1car.com/library/battery_disconnect_problems.htm
Tester
The humming and whirring went away after I changed the oil. No clue what the relationship between the humming and the new oil is though. Glad it went away!