2004 Chevy Suburban 2500 with the 6.0L engine. It’s started this rattle at idle and under load at low RPMs. Idling it’s hit and miss, under load it’s steady. Moves up and down with RPMs. I was worried enough to cancel the trip to town. Is this a rod knock? Exhaust leak seems unlikely. Maybe lifters?
This engine has seen some abuse, uses a bit of oil. Good oil pressure, not overheating. Runs good otherwise and the noise goes away at driving speeds… Or at least I can’t hear it.
See the video. I run it some under torque lock (in gear with brakes on) and some in park. Definitely louder under load. The hit and miss aspect is what throws me off… Doesn’t seem like a rod knock would do that.
Chris it sounds engine external to me.
These have a trait of snapping off one or more engine exhaust manifold bolts with age.
Then a noise that comes and goes with exhaust manifold heat changes and engine torque twisting.
Listen up through the wheel wells. Louder?
Can happen at the same age, on both sides; confusing.
Yes; hard to do; but visually look for any missing bolt heads.
I would have said maybe an AFM camshaft lifter buggering up on you, if it had sounded engine internal. Heavier chassis 6.0L like my 3500 and the 4500’s did not use the variable cylinder systems . . .
Yours I am not sure.
Steve Unruh
