Just picked up an 08 H2. When I first drove it, it was hot out and there was no noticeable piston slap but now that it is cold it is very noticeable. Literally sounds like a diesel until the engine totally warms up. I have heard that this 6.2 was prone to piston slap and it is nothing to worry about. Anyone else experiencing this? Is it something I should be worried about. Seems louder than piston slap that I have heard before. One guy told me it was rock knock but I don't think rod knock gets quieter as the engine warms. Truck has 85K on it. Thanks guys!

 

Change the engine oil asap. Refill with a quality full synthetic oil. GL

 

what's the oil pressure look like when its cold?

 

It is at 40 when cold. The only time I see it drop down to 20ish is after I have been driving for like an hour. And that it onky at idle.

 

I would start by looking at the lifters first, the lifter plungers will stick down in the lifter bore a little and until the engine warms to take up the slack it will sound like you say.

There are tons of videos on this issue on youtube concerning the LS engines and stuck lifters

Neal

 

You sure that it's not broken exhaust manifold bolts causing an exhaust leak that seals up once warm?

 

I dont think so. I know what that sound is.

 

my 08 had the same symptoms, on cold start I would get a tapping sound and after warming it would go away and depending on how cold it was the noise was very light or heavy.

I removed the valve covers when cold and had a few push rods with slack with the cam on the base for those lifters, I also used a bore scope and inspected all lifters, of 18 around 10 lifter plungers were stuck down in the bore to differing degrees.

The piston slap issue with the LS engines started back in the beginning of the LS equipped vehicles, GM changed up some design issues to address this. The pistons in the L92 are coated with a material to reduce drag and wear on the skirts so I would say that piston skirt slap is no likely but not unheard of.

In my opinion the 1 flaw left with the LS engine is the lifter trays that are used to prevent the lifters from rotating, they funnel a large amount of oil from the heads right down on top of the lifters washing any solids down on top also contributing to the lifter plungers sticking from foreign contaminants.

I pulled the engine out of my H2 and tore it down to check all tolerances, everything was good except the cam brg clearances (a known issue with the LS but not detrimental). The cylinders were very close to as built condition along with the piston skirts. The friction reducing coating on the piston skirts had worn a good bit on the skirts of the pistons that were to the lower side of the bore but was not completely gone.

Neal

 

Thanks Neal! I appreciate all of the info. I do have an 05 Tahoe that I has the lifter noise but this is louder. More like a knock. In google searches I have found people with 08-09 Denali's that are describing exactly what I am experiencing. I had also test driven another 08 H2 before I bought the one that I have and it did the same exact thing. Basically sounds like diesel when cold and under load.

Sounds almost exactly like this around the 30 second mark. More noticeable in person though.