['04 VZ SV6] Rattle Noise(s) When Stationary Revving

[Dechlan Tutty]

Hi everyone,

I heard a rattle when pulling away from a light with the windows down today, and tried to replicate it when I parked (which I was able to).
It sounds like an exhaust/metal-on-metal rattle when revving, but only occurs when on the throttle. After letting off, the sound goes away. When the motor cooled down I tried moving the manifold heat shields by hand and they didn't move.

When letting off, if revved hard enough, there is a slap sound (best way to describe is "pap") that happens once.

Any suggestions?

I understand this is very brief, and I will get some sound recordings tomorrow, but I thought someone might have an idea of the sounds.

Cheers, Dechlan.

 

[99notout]

Cat has broken up

 

[Skylarking]

Cat breaking up will sound like shaking a can with rocks in it. Such would occur is there are other engine issues (faulty spark plug for example) that overheat the cat substrate causing a mechanical failure of the substrate itself. Such would be accompanied by a DTC...

But if the substrate has only a small bit broken off, you can remove the cat and shake the loose bit out and that may be enough. You’d still need to fix the underlying DTC issue that caused the cat substrate to fail.

As it (the noise) just started (and you have no DTC’s), I’d think it’s some heat shield bolt that is loose or maybe a cracked heat shield near a fastener. Both may not be apparent when things are cold.

 

[lmoengnr]

Check all your heatshields, give them a tap with a hammer handle, listen for a rattle.

 

[wannaeatyourbrains]

Check the 4 hangers in the back. Will be movement if they have stretched. Slaps the cradle on start up and take off, especially if your engine mounts have been in a while.

 

[Dechlan Tutty]

Hey guys, thanks for the help and suggestions. I tried moving the hangers by hand, and the exhaust moves a little bit, but not what I would've thought to be excessive. It certainly doesn't hit anything in the couple mm I can move it, but maybe it's different with the engine revving.

I tried to record a video of the sound, but couldn't replicate it, but I got a video of the slapping sound I was talking about.
Here's the video:

Thanks again for the help!

 

[wannaeatyourbrains]

Sounds like a cracked or loose engine mount. Maybe it got overtightened. That makes them break. Someone had at it with a rattle gun instead of a torque wrench.

The bolt can crack out of the mount. Then they are hard to get out, because the bolt will just turn when you try to undo it. You might have to drill it out. Try tightening them. 19mm.

If it turns, it is rooted, and the mount base will be moving up and down a centimetre or so every time you rev it. Do you hear it every time you take off?

You can also jack the engine up from the torque converter and see if the mount base is lifting a tad.

It is a really nice car. Auto has its advantages. One hand free for food, phone, girlfriend, whatever... Looks so sharp.

Maybe check the k-frame bolts are tight too while you are under there. It definitely seems to be associated with engine movement, the engine returning to position after revving.

 

[Dechlan Tutty]

Sounds like a cracked or loose engine mount. Maybe it got overtightened. That makes them break. Someone had at it with a rattle gun instead of a torque wrench.

The bolt can crack out of the mount. Then they are hard to get out, because the bolt will just turn when you try to undo it. You might have to drill it out. Try tightening them. 19mm.

If it turns, it is rooted, and the mount base will be moving up and down a centimetre or so every time you rev it. Do you hear it every time you take off?

You can also jack the engine up from the torque converter and see if the mount base is lifting a tad.

It is a really nice car. Auto has its advantages. One hand free for food, phone, girlfriend, whatever... Looks so sharp.

Maybe check the k-frame bolts are tight too while you are under there. It definitely seems to be associated with engine movement, the engine returning to position after revving.

Thanks heaps for the feedback and info.

I'll have a look over the weekend as I'm away for the week now us regional Victorians are allowed to leave the house a bit more. In the car, it sounds much quieter, and I only heard it because the song changed over and there was no real interior sound and the windows were down. It doesn't seem to do it all the time, and again, only makes a noise on decel/gear changes (basically when the motor rocks back a bit, like you said).

Yeah the auto box is growing on me a bit, and I'm quite happy with the looks of the car now. I've tried to just do a couple of little clean-up things and leaving the running gear pretty much stock (it is only a V6 at the end of the day). About the only thing I've done/going to do, as I'm a big fan of stock cars, is a transmission cooler as I've heard mixed opinions from some people that the 5L40's like to get a bit hot, and the PCV mod.

Thanks again.
Cheers, Dechlan.