4.8l chevy knock

engines
chevrolet
noises

#1

2009 chevy silverado 4.8l v8 crew cab 4x4

Got in my truck after work and started hearing a knocking noise. The noise seems to be every second and as the motor warmed up it wasn’t as loud at first.
I live about 4 min from work. By the time I was home it wasn’t loud. While trying to find the location of the noise with a stethoscope i noticed it louder on the passenger side near the top of the engine on the front coil pack. Also just noticed and it may have always been their but the intake makes a “poof” sound when the truck is turned off.


#2

Does the noise increase with engine speed? If so, without hearing the noise myself, my best guess would be a sticking lifter. Although a lifter makes more of a tick sound than a knock. Lots of time lifter noise will sort of come and go. My experience with it, the lifter would stick in an old Chevy 350 I owned, as the engine warmed up the lifter would free itself and the sound would go away. Sometimes the sound would come back on a cold start, other times I wouldn’t hear it. Generally, once a bottom end knock starts, I don’t think the sound will ever go away.

How many miles on the truck, and how long between oil changes?


#3

I really hope you drive the v8 crew cab 4x4 truck more than that, That is about the worst thing you can do to a truck.
If that’s all you drive it you’re not changing the oil often enough.


#4

Wouldn’t you have to know how often he changes the oil to know that he isn’t changing it often enough? Or did he mention that and I overlooked it?


#5

The 4.8L/5.3L LS engines have been known to develop piston slap, particularly when cold. When the engine warms up it will lessen/go away. Nothing to worry about at this point


#6

Agree with the piston slap. Although I thought it showed up fairly early or didn’t show up at all. I also read that GM addressed it somehow in 2004, but I can’t remember where I read that or what they did to address the noise.

I was hoping I was correct on that. My 2005 4.8 doesn’t have piston slap (yet) at 140 something thousand miles. Am kinda hoping to avoid it. Even though it isn’t harmful, it doesn’t sound too sporty.


#7

A loose spark plug could cause this symptom.