the_thunder08

Hello, I was just wondering why my 2000 sliverado (5.3) sounds like it has a knock or piston slap when I first start it and take off, oil pressure is around 60 lbs when cold then goes to around 45-50 when warm. I usually let it run for 2 to five mins before I go but it still makes the sound but only for about 1 min then it goes away.

02Z71silverado

yeah same thing for my 02' 1500. when its cold and first starts up, take off, it almost sounds like a diesel engine. i asked my auto shop teacher whose been a chevy enthusiast for years now and he said all the older trucks do it when they're cold. didnt really have an explanation as to why it does it but it shouldnt be anything to worry about.

the_thunder08

thanks, thats what i thought.

ax7221

Whats the temp of the outside air during this cold start? is it possible that the heads are actually a little shrunken from the cold but once up to 200 degrees fill the cylinder? a few hungred degrees (like say from 30 degrees outside to 230 running temp) could make the metal expand enough to fill the cylinder so the head isnt tracking weird. Kind of like when you heat or freeze metal parts to be pressfit together.

02Z71silverado

i suppose that is possible. good thought

sierra_5300

go to www.pistonslap.com find out all the info you need it was a poor design on gm behalf i had a 2002 it had it real bad all the time not just when it was cold. problem was not fixed until late 2004 like december even unitil this day all of the 4.8,5.3,6.0, and have some noise but it is extremely quiet they put a coating on the piston skrit to make it quiet i have a 06 and every now and then it will have some piston slap noise but it is extremely quiet like i said. i have an ear for that kindof stuff