Help Diagnose Loud Rough Grinding Noise under Hood at Idle

[Fischer]

When sitting in wither D or R I have a horrible noise under the hood. I can't seem to locate it exacly but it sounds like a dry bearing or grinding noise.

I just cleaned the MAS and the IAC. I am wondering if this is the IAC and it's needing replacing?? Or a clutch or pully bearing going bad...Only really prevalent in D or R not so much in Neutral.

Any help would be great!

 

[Lifted95X]

Tensioner maybe....mine sounded pretty nasty when the bearing started to go.

 

[Fischer]

Possible...but why would it get worse in D or R. That is when it really gets loud.

 

[Lifted95X]

mine did it to...just the same...I don't have the slightest idea why...but mine was always louder with it in drive or reverse with my foot on the brake, than it was in neutral.

 

[Fischer]

I'll have to give those a check. POssibly borrow the girlfriends stethescope for nursing.LOL

 

[punkbek3886]

this exact same thing happened on my moms bonneville. it turned out to be a faulty "harmonic balancer" aka a sort of counterweight on the crankshaft pulley. it made the sound at low rpms but it went away when the engine was revved up. it sounded like the engine was done for. hopefully this will help you.