Engine noise.

[SpareParts]

My engine has a noise and i can't decide what it is. It is not a rod or crank knock. It is not in the bottom end. It is only 1 cylinder and only when cold. It goes away when the engine temp reaches 190ish on the temp gauge. Engine runs fine otherwise. Idling cold you can't hear anything. You can hear it when accelerating before it's up to temp but when you let off the throttle the noise stops. It is on the DR side.
The noise has not gotten worse in about 5k miles that i have owned it.
It sounds like either a bad case of piston slap or a wrist pin.
I would think piston slap would stop after a minute or so but if a wrest pin it would never go away. Maybe carbon buildup between the head and piston?
I do have 2 broken exhaust bolts, one in the front location and one at the very back. I don't see any carbon that would indicate a leak. The noise sounds to metallic for an exhaust leak but im not sure because i have never heard the famous LS exhaust leak noise.

Any thoughts?

 

[strutaeng]

Hard to tell. Maybe make a video on YT and then post the link here?

For sure, the broken exhaust manifold bolts need fixing.

Piston slap I think for some reason only affects the 5.3, not the 6.0 or 6.2? Not sure. My L59 makes some piston slap noise for the first 20-30 seconds in the cold months. Nothing in the warm months like right now. Otherwise it runs very quiet and smooth.

Another thing you can do is get yourself a HF stethoscope and poke around the engine to see if you can pinpoint general location of the sound.

 

[Marky Dissod]

Piston slap I think for some reason only affects the 5.3L, not the 6.0L or 6.2L?

Aluminum block, lightweight pistons with short skirts, and cold piston-to-cylinder tolerances, all spec'd to improve fuel economy,
give the cold piston a wee lil bit more room to waver horizontally in the cylinder - forward or backward or side-to-side, or combinations thereof.

5.7L & 5.3L pre-'05 were most likely to cold start noisy; in '05 piston design spec was updated to minimize the issue.

 

[j91z28d1]

even if you. don't think it's the manifold bolts, the clamps are cheap, work and work will. can be a hassle to install. but worth it in the long run and will rule it out.

 

[Joseph Garcia]

My engine has a noise and i can't decide what it is. It is not a rod or crank knock. It is not in the bottom end. It is only 1 cylinder and only when cold. It goes away when the engine temp reaches 190ish on the temp gauge. Engine runs fine otherwise. Idling cold you can't hear anything. You can hear it when accelerating before it's up to temp but when you let off the throttle the noise stops. It is on the DR side.
The noise has not gotten worse in about 5k miles that i have owned it.
It sounds like either a bad case of piston slap or a wrist pin.
I would think piston slap would stop after a minute or so but if a wrest pin it would never go away. Maybe carbon buildup between the head and piston?
I do have 2 broken exhaust bolts, one in the front location and one at the very back. I don't see any carbon that would indicate a leak. The noise sounds to metallic for an exhaust leak but im not sure because i have never heard the famous LS exhaust leak noise.

Any thoughts?

I've got the same sound on my 2007 Yukon XL Denali, and its been that way since I bought it new to me 7 years ago. My 1997 Yukon (RIP) had the same sound situation. Nothing has changed since, and the only thing that I do is is baby the truck, until it comes up to operating temperature.

I will say that the sound is much less, since I substantially bumped up my oil pressure.

 

[SpareParts]

I've got the same sound on my 1007 Yukon XL Denali, and its been that way since I bought it new to me 7 years ago. My 1997 Yukon (RIP) had the same sound situation. Nothing has changed since, and the only thing that I do is is baby the truck, until it comes up to operating temperature.

I will say that the sound is much less, since I substantially bumped up my oil pressure.

Yeah, i do the same.
Baby it till up to temp and the noise is gone.
Mine has not changed since the day i bought it even after changing the oil pump and O ring.
I think it's a really loose piston. Surly a wrest pin would have let go by now i would think but i never push it past 5K rpm.
I have also adjusted my shift points to 5K under WOT.

 

[Foggy]

Piston Slap - common on your engine... Like you said, baby it
til temps are up a bit. Happy Driving