4.6 metallic rattle at 2000 rpm or under load

[rtk11]

I think I know the answer... but holding out hope that maybe the noise may be something else.

My 2002 EB 4x4 has 250K miles on the 4.6. Around 2000 rpm in neutral, I can almost always replicate a metallic rattle. When under load, I can hear at this rattle. (Under moderate to hard acceleration or if driving up a hill). I just changed the oil and filled all the way up to the upper hole on the dip stick (about 6.5 quarts) and that seems to have quieted down the noise, but it’s still there.

What does everything think? Any chance it’s a lash adjuster? Or is it rod knock (which is what I’m fearing.)

 

[07gtman]

The timing chain guild could be worn out.It's nylon/plastic

 

[ROBinGa]

And you’ve already ruled out a vibrating heat shield around the exhaust pipes right? I had one of those that developed a hairline crack and it only rattled at certain rpm when it was really serious sounding until I bent it where the pieces wouldn’t touch and vibrate. Seems odd your rattle if it is an internal condition doesn’t do it all the time.

 

[07gtman]

And you’ve already ruled out a vibrating heat shield around the exhaust pipes right? I had one of those that developed a hairline crack and it only rattled at certain rpm when it was really serious sounding until I bent it where the pieces wouldn’t touch and vibrate. Seems odd your rattle if it is an internal condition doesn’t do it all the time.

I also have a exhaust rattle sounds just like a knock, I'm missing the first rubber grommet on the exhaust bracket drivers side..

 

[rtk11]

Thanks guys. I took some tubing and listened to the timing chain cover (no knocking noise, just the whir of the chain on the sprocket) so I’m thinking that’s not it. I did the same to both valve covers and also no sign of any unusual sounds. I am pretty confident it’s not a heat shield as I replaced my catalytic converters with a Magnaflow direct fit catalytic converter kit. I ensured that none of the heat shields were loose or touching the catalytic converter (just so I knew that I could rule out this sound). I also had the transmission rebuilt and the flex plate checked to ensure no cracks.

Not sure about the exhaust bracket and the rubber grommet? Is this the rubber donut on the hangar? If so, I am OK there as well.

I’ll take another look tomorrow, but I do know that the noise is pretty prominent by the bell housing, which is what’s leading me to the rod knock theory.