after putting coolant in the oil of my 5.3 i swapped in a 6.0. since then i have suffered the oops i forgot a ground, crappy brand new water pump, squeaky belt, new alternator and holy **** moment of my oil pressure disappearing ,must have been cluster or sensor. but now i have this weird cracking sound at cold start up , like a walnut cracking. only a little, short duration and not really rhythmic. sounds like it's coming from the balancer area but it's hard to tell. i did reuse a set of plugs, wires and exhaust gaskets. i tuned the truck and it pulls like an animal. any ideas?

 

so have you fixed all the previous problems that you listed? and does it make this noise everytime you cold start it?

 

yeah i fixed all of the other stuff and the sound is pretty much every cold start. 30 seconds or so. i am just trying to debug this. i just got off the phone with a guy who has a lq4 for sale for silly cheap who said his new motor does the exact same thing. it's upstate ny so cold start now is 40*F

 

Piston slap!
6 liters were known for it on cold starts

 

So were 5.3's - The 99-01's were the absolute worst, my dad's would echo in the garage.

 

I guess this is while the engine is running? I have clicking sounds BEFORE a cold start, which is the fuel pump relay spazzing out....damn electrical gremlins

 

yes when its running. it sounds like it's trying to pass a stone. seems to be less now.

 

My 00 sierra with the 5.3 piston slaps on a cold start, common issue on the Gen3 small block.