Grinding type sound [Archive] - Forum


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11-05-2013, 09:33 PM
Wondering if anyone can help me determine this strange noise that has developed in the past few days...The noise is only heard while accelerating hard, starts in around 3000rpm, at first i hear a slight whine, than it almost sounds like a metal on metal type grinding sound till about 4500rpm or when i let off the gas. I dont wanna push it any harder in case its serious. It will not make this noise in park or neutral, only when the motor is under load. Within the past 8 months i have replaced the belt tensioner, the idler pulleys, water pump, and the belt itself. I also replaced the alternator within the past year, with a H.O alternator from db electrical. Has anyone had an alternator go bad that would make a sorta grinding sound under load? possible bearings going bad? Any input would be great, thanks!

11-06-2013, 05:15 AM
Have you tried opening the throttle manually with the hood up while listening for the noise? Doing that should help narrow it down and locate the source.

11-06-2013, 12:13 PM
Yep tried that and still nothing. The noise is only there when the engine is under load. I had a tech take it for a drive and he thinks it could be the bushings/bearings on the alternator. Just stumped as to why I cant hear it when I rev the motor, but as soon as I drive it the noise is heard.

11-06-2013, 12:23 PM
Depending on how severe the noise is, you might want to look into a possibly faulty torque converter or flexplate.

11-06-2013, 12:43 PM
The noise does sound like its coming from the top of the motor near the alternator. If the bearings were going out in the alternator could that be what im hearing? Its like a metal on metal rubbing sound.

11-06-2013, 04:58 PM
Take the belt off and spin the various accessories by hand. Each should turn smoothly with some resistance, and there shouldnt be much if any play in each pulley. If any of them spin freely for more than a rotation or two then the grease in the bearings is probably gone. If any are hard to spin they are also bad.

Only making the noise in gear makes me suspect transmission or beyond though.

11-06-2013, 05:22 PM
I noticed the alternator pulley to spin alot more freely than the others. And also noticed a little bit of play on the power steering pulley and more resistance.

11-06-2013, 10:41 PM
Wow, well I fixed the problem. I had my car in the shop prior to this strange noise, and come to find out the shop put my strut tower brace on wrong. The grinding sound was the alternator tilting back just enough to rest on the brace causing the sound. Thanks anyways for the input!

11-06-2013, 11:10 PM
Glad you got it fixed!

There should be more resistance on the Water Pump and the Power Steering pulleys just because they are both spinning a shaft in fluid. The alternator tends to spin a little easier because there's more mass moving, and not much resistance against it without anything drawing power from it.

The engine moving backwards in gear would definitely make sense, I'd personally get a flashlight on the transmission mounts to make sure they aren't torn/damaged, as the motor really shouldn't move around too much.