Metallic rattle under load.

[ohno06gt]

My 2006 Legacy gt has developed a weird sound. When the car is under load around 2-3k it makes a metallic rattle, almost like a spitting sound, it's hard to describe.

Can't hear it unless the windows are down and I'm driving next to a wall or other cars. All the heat shields are tight and I don't see anything making contact where it shouldn't.

 

It doesn't make the sound when revved in park/neutral or when it's torque stalled. Car still seems to run and drive fine and makes plenty of boost. I get no feedback knock or fine learned knock at all.

 

All fluids are pristine and at their proper levels. A used oil analysis was done 500 miles ago and came back perfect. I was leaning towards a cracked header or up pipe but would think it would struggle to make boost.

 

I'm thinking about taking all the heat shields off for a more thorough inspection but the bolts are pretty seized up.

 

Anyone have ideas or a direction to head in? I tried my best to capture it on video this morning, the sound starts about 1/3 into the clip.

 

https://youtube.com/shorts/VfkVTZXwiUU?feature=share

Edited April 14, 2022 by ohno06gt

[Max Capacity]

Hard to tell from that.

 

Have you grabbed the CV shafts and see if there is free play in them ?

 

How are the wheel bearings ?

[ohno06gt]

CV axles seem good, they were replaced 7-8k ago with ones from raxles and don't have any play.

 

Pretty sure the wheel bearings are ok. When grabbed from 3 and 9 o'clock/ 12 and 6 o'clock there is no wobble. It seems more rpm dependent than speed.

 

If there was a crack in the header or up pipe would it still build boost fine? I saw no soot around any exhaust flanges or gaskets but not sure about under the heat shields.

[ttnio]

those shields on the exhaust oem system makes a lot of rattling sound when they deteriorate... time for lift .

[aero901]

A/C Clutch dragging? Belt idler pulley bearings? Vacuum leak somewhere? Couldn't really make out the sound in the video...

[ohno06gt]

Still haven't been able to figure out this rattling sound. It seems very rpm dependent and stops when in boost above 2 psi or so.

 

Almost seems like the frequency of the rattle coincides with the pulsing the ebcs makes at higher boost.

[Marvick08GT]

Tighten the rod for the wastegate. This is a known problem.

Had the same issue.

 

What turbo do you run? How much boost are you seeing?

[ohno06gt]

It's a td04hla-19t (jdm twinscroll) built by hcfi. Maxes out around 19.5 psi. I'll have to dig around for info on tightening it but seems pretty straightforward. I always suspected it was the wastegate.

[ohno06gt]

Tighten the rod for the wastegate. This is a known problem.

Had the same issue.

 

What turbo do you run? How much boost are you seeing?

 

 

Thanks man that was the issue. Tightened the arm one full turn and saw an improvement so tightened it another full turn and it's almost gone. Hasn't over boosted but keeping an eye on it. Right now it's tolerable but may go another half turn to see if it completely stops it.

[Marvick08GT]

Usually you are good for a few turns. I always did about 8 xD. Just watch the spike, should be fine.