Rattle at idle in gear

Added my own video:

Does it happen when the engine is hot and cold?
How many miles on the engine?
What viscosity engine oil are you using?
Can you tell from what area the noise is coming front? Front, rear, under, etc.


As a 1st step, I recommend to remove the serpentine belt and then start the engine to see if the noise changes.
Also remove the plastic engine cover to see if it helps in narrowing down the noise.

CalgaryTSX said:

Does it happen when the engine is hot and cold?
How many miles on the engine?
What viscosity engine oil are you using?
Can you tell from what area the noise is coming front? Front, rear, under, etc.


As a 1st step, I recommend to remove the serpentine belt and then start the engine to see if the noise changes.
Also remove the plastic engine cover to see if it helps in narrowing down the noise.

Click to expand...

It happens both hot and cold.
The engine has just under 100k miles.
Its whenever the car is idling, sitting still, but either in "R" or "D" not in park nor neutral, and not while moving.
When i first start the car, sounds fine, the second i shift into gear i hear it, then it goes away as i start driving.
5w-20 full syn

it sounds like its coming from the belt side of the engine, tough to tell if its up top or lower.
I can remove the cover, Ill try to get under her tonight to see if its louder or quieter below.

I think the more curious part, is why at idle, and only in gear, and not while moving, nor when in neutral or park.
That part just doesn't make sense to me.

So i took off the serpentine belt, started the car, put in gear, no noise. Tried a few times. Put the belt back on, start the car, put into drive. noise is back. So it has to be belt/pulley related. Its a brand new belt and tensioner, unless i got a defective one... I checked all pulleys, none of them have play, also there is no visible wobble. Any other ideas? I put a screwdriver up to each component and listened (red neck stethoscope) but couldn't isolate the sound.

thinking it may be the a/c clutch starting to go. I thought that yesterday, but it turning on/off a/c only seems to impact slightly, maybe the clutch is just starting to lock up here and there, going to try it.

Since the noise goes away when the serpentine belt is removed that is great news.
This means it's not an internal engine issue or an auto trans issue.

I've never worked on a 2nd Gen TSX. There must be a belt tension indicator on the tensioner like a 1st gen?
Is the tensioner moving a lot when the engine is making the noise?

If the tensioner indicator shows that the belt is slightly on the loose side, perhaps a slightly shorter belt will reduce the noise. ie. increase the tension on the tensioner, which in turn increases the tension on the belt.

I did this exact thing on a 1st gen TSX many years ago after aftermarket pulleys were installed.
The spec'ed belt that came with the pulleys was a little too long. The tensioner was vibrating, a shorter belt fixed it.

So, I was out of time diagnosing this, also don't have a lift to get under it. Since the noise only happens in gear at low idle, wasn't climbing underneath. I took to my local shop. They are convinced the noise is coming from the oil pan area. They think its low rpms and when the engine is under load. Just don't understand why that specifically is causing this. I read some forums saying this could be the oil pump chain tensioner, i think theres some fancy name for it, but the mechanic thinks its too loud to be that. I guess there's a chance it could be a crank bearing starting to go out? just seems weird that it runs and sounds great, just how a low idle rattle. Any other thoughts? I could drop the oil pan but don't have a lift and not sure its worth it...

Can you tell from what area the noise is coming front? Front, rear, under, etc.