So here’s the dealio thats driving me crazy. When the cars cold or even random times I get this clicking from the left lower engine compartment. What’s very strange is it doesn’t start until I turn the AC on AND put it into gear, D,N,R anything. I turn the AC off now the noise will remain. I’ve already did a valve adjustment...twice as the first time I yielded to the high tolerance and the gaps never closed and was chatty so in I went and went mid and that worked so it’s not that. It also doesn’t coincide with the rpms, it’s just a one speed rattling noise that disappears in a higher rpm like 2.5k and up. I thought it may be the idler Assy as I had my wife do the magic as I listened with my stethoscope and it was loudest on the arm, changed that out. Not it but I’m sure it was good to do anyways. Is there anything anyone has seen get loose like a bolt somewhere? I’ve literally been everywhere under the engine and the above mentioned to make it start just seems f***ing crazy and my ocd is in 6th gear lol. Thank you all for anything you got.

 

Serpentine belt recent?

 

Yeah that was first about a few months before the noise though.

 

You stated that noise seemed to be coming from lower front left (driver side) but then when using your stethoscope you were on the right side ?
So far you have replaced the serpentine belt and auto tensioner assembly? Suggest slipping the belt off the pulleys enough to where you can spin the water pump and alternator pulleys. Check for drag or lateral movement of those pulleys. Perhaps bearings failing in one of those parts?
Also model year, miles, and transmission type ?

 

That sounds about right to me.

 

that doesnt sound good

 

fit09's suggestion sounds logical, if you're not comfortable doing that, then perhaps more details would help.

it may just be the noise the ac compressor makes..

unfortunately onomatopoeia only conveys so much sound. can you record the noise with a camera and post it to youtube, then link? it will help to include: startup sound, ac off idle, and ac on idle? (both while cold and warmed up).

 

The first question I would need to ask.....Lower left is the drivers side, is that where the sound is coming from?

 

vid/audio recording will help. descrip makes it sound like increased engine load is creating body panel/cowl vibration (unless something was left loose). I'd check out the clippies on the plastic undercowl, but more specifically, have you removed or ever impacted your front bumper?

This spot right here can create a rapid click. Damaged bumper clips. the plastic bumper vibrates against the metal body panel.

 

I had the same issue after overcharging my AC system, try listening near the AC compressor at the bottom of the car