Rattle coming from under hood...in time with engine speed.

Vehicle is a 2011 with the V6. Since last year, the vehicle has had a groaning sound when idling and accelerating. A mechanic at a shop i've used suggested it might be a bearing sound coming from the drive pulleys.

Tonight, there is now a chattering sound coming from the front of the motor. It sounds like cards stuck into the spokes of a bicycle wheel that kids used to like to do. The sound is not just on acceleration like most of the posts I've searched. The sound increases with rpm. It is as clear on idle as it is under higher rpm's, its just faster.

I'm wondering if there's an idler pulley or more that I should be looking at.

 

I would def look at the pulleys. Spraw some wd on each and see if it goes away for a bit,dont go crazy though.

 

Pull the belt off and check the pulleys for binding or excessive play.

 

Sounds like a plan! Thank you!

 

OK, so listening to it, its a clattering sound, coming from the driver side...I'm wondering if either alternator or AC compressor. When i turn AC on or off inside the cab, there is no change of sound. I'm not sure if the water pump makes that sound, but its almost really further left. Do alternators make a rattling sound like that? Would a stethoscope help in this regard?

Pulleys make more of a squeeking sound from what I understand.

 

You can use a mechanics stethoscope, or a piece of pipe to narrow it down.
Thats how I narrowed down my bad alt.

 

I'll get a stethoscope. Cheap enough at HF I guess. If it craps out, I'll use a long screwdriver. I did read that "turned out to be the top most #2 idler pulley was totally shot. It wobbled a bit on its axis and the bearings were completely toast. Sounds like a can of marbles." So, I guess it could still be a pulley. Off to HF.

 

Stethoscope gotten. Good advice all around. Put it on AC but it really wasn't making that chattering/marble sound. On alternator...bingo, marbles are making noise. Options are seeing about having this one rebuilt, getting a new/rebuilt one or buying a used one. I really don't want to let this one go so if they can be rebuilt, I'll go with that. I'm going to see about interchanges from another vehicle to see if I can get one from the local Pullapart...

 

Oh yeah! I'm going to replace the serpentine belt and the pulleys while I'm taking the time to do this along with alternator.

 

Sounds ridiculous but check the hood prop rod..... Former car had a fkn rattling that I couldn’t find for the life of me and a mechanic buddy couldn’t either. Then once again I opened the hood to look and actually used the prop rod, rather than a 2x4 I have in the garage that I commonly use for the purpose. That’s when I found the plastic clip that holds it in place was broken....

 

sometimes its the pulley tensioner spring is weak and that will rattle or I think they have a timing chain/belt tensioner also its like a valve lifter that can also rattle. My 98 used to do that when I needed an oil change.

 

keeping this one updated for someone possibly doing a search later on. Took the alternator out. Had it tested at Advance. They spun it up, tested good, no sounds at all. Very quiet. So good news is I learned to take the alternator out and the alternator is good. Bad news is the alternator is out and needs to be reinstalled. Good news is I can get at the pulleys from below and above now!

 

Did you ever figure out this issue?