4.8 engine rattle at start up

[bennyk]

On cold engine start up I get a loud engine rattle that goes away in about 5-10 secs...hard to determine source...could it be the EGR valve?? or multiple lifters?? Benny

[mjgjr72]

this will not help but

gm says a slight cold knock or piston slapping noise is considered normal if not present after the engine reaches normal operating temperatures.

well thats what they told my buddy he has a 5.7, this also happens on some 5.3's, and gm will not due anything about it.

how many miles are on it.

[bennyk]

Originally Posted by mjgjr72

this will not help but

gm says a slight cold knock or piston slapping noise is considered normal if not present after the engine reaches normal operating temperatures.

well thats what they told my buddy he has a 5.7, this also happens on some 5.3's, and gm will not due anything about it.

how many miles are on it.

Howdy, I have about 76,000 miles on the truck, mostly hi-way...Used to get just a bit of lifter tap before but the last few days it`s been like a diesel on start up but clears up very quickly....About a week ago I changed from Pennzoil syn. to Mobil 1 syn. but can`t see that as the problem.unless the place doing the oil change changed the viscousity severly...Hmmm....Benny

[mjgjr72]

do you know what types and viscosity
kind of odd started shortly after oil change
maybe penzoil was 5 or 10w-30 or 40 and the mobil 1 is a 0w-30 or 40 and lifters are draining down more than before