Need Advice: 2009 5.3 Silverado engine knock question

[STech]

I have a 2009 5.3 Silverado Z71, Since new I have a weird noise that I cant pin point exactly where it comes from.

When starting the truck after it has sit for 1 to 2 hours I get a semi loud knocking sound kind of like piston slap but just a little different. It lasts for approx 2 to 3 minutes. It is not there at all when starting from cold in the morning, or sitting for a long period of time, only after its been driven and then sitting for an hour or so. The dealership is stumped, they have heard it a few times now but just cant pin point it.
I seem to pick it up with a stethoscope the best at the oil pump or on the side of the block at the #1 cylinder area. But again it doesn't do it on first start in the AM.

Anyone ever hear of this or have any ideas.

[kahjdh]

Wow, interesting. Is it a gen 4 motor?

[j cAT]

Originally Posted by STech

I have a 2009 5.3 Silverado Z71, Since new I have a weird noise that I cant pin point exactly where it comes from.

When starting the truck after it has sit for 1 to 2 hours I get a semi loud knocking sound kind of like piston slap but just a little different. It lasts for approx 2 to 3 minutes. It is not there at all when starting from cold in the morning, or sitting for a long period of time, only after its been driven and then sitting for an hour or so. The dealership is stumped, they have heard it a few times now but just cant pin point it.
I seem to pick it up with a stethoscope the best at the oil pump or on the side of the block at the #1 cylinder area. But again it doesn't do it on first start in the AM.

Anyone ever hear of this or have any ideas.

I would demand they send the engine oil out to be tested for metals....could be main bearings or piston issues ..this is typical of a noise that is temperature sensitive ..

also oil pressures what are you getting ?

[kahjdh]

Gen 4 meaning MDS or DOD?

[Retiredgunner]

Isn't this noise called piston slap?