Roland Herrera

Hi all, I inherited my 2008 TL 3.2 a while ago, and recently have had some issues with this noise:
This noise happens on cold starts, and is the loudest when I am in reverse, and continues when I give it some gas. I believe it is related to another noise that I have, which is a similar sound, but with more of a "knocking" quality to it (a literal knock, not engine knock) that happens after a cold start when I drive and then let off the gas (but don't apply brakes) at most speeds. The noises go away eventually, and often I can't get it to make the noise twice in a day, except for when the car is on a slope (both nose down and nose up).
I asked some guys at work (I work at a service center as valet) and they suggested cleaning the throttle body, but I would think the throttle body would make the noise always, not just on a cold start.
The car has somewhere along the lines of 180k miles on it, and recently has had the oil changed and the transmission fluid flushed and replaced (to try and remedy the issue, which it didn't).
Any ideas before I have to shell out for a diagnosis and find a way to get to work while it's in the shop?

viperkorn

Is the sound louder inside or outside of the car? A/C on or off? Checked your belts and pulleys? First find out at least the area the sound is coming from. use a stethoscope If you do not have one an old hose you can cut will work. Engine mounts good? I had a brushing noise in my old Cadillac turned out some crap worked its way into the a/c fan. Location where the sound is loudest would help everyone help you.

Roland Herrera

The sound is definitely louder from inside the car, and persists with the AC on or off.
Inside the car it sounds like it's from just in front of and under the shift knob. The last time I tried to just listen for it by ear with the hood open I couldn't hear the sound over the rest of the engine going, but the hose idea is a good one, I'll try that one of these mornings before work. Once someone else gets home I'll have them check to see if the engine moves a bunch when I change gears.
Thanks for the suggestions!

guitarplayer16

iTrader: (8)

Check for anything that could be loose, I found my PS reservoir lying on the belt and the belt almost ate through all the plastic before I caught it.

Common cause of knocking is worn pulleys, remove the belt (in the morning for cold start) and see if the sound goes away.

LGcbp8

I agree, check the pulleys. And check the alternator. It could be on its way out and making some feedback noise.
For the knocking noise, check your cv boots and suspension bushings, tie rods, etc...

What does the noise sound like 1st start of the morning in the engine bay? Post a vid of a cold start with the hood popped.