I have a 2001 vette with 68,000 miles and purchased it 6 months ago. I have noticed a knock, like no oil, when I start my car when it is around 40 degrees outside. I trying to find out why it is doing it. I checked the oil level and it is a little over add. Can there be a problem with the oil pump? I use 5w-30 mobil oil.

 

It is probably "piston slap". Common in some LS1 engines. After the motor warms up it is O.K. Do some research and you will find a lot of info.

CG

 

I seem to have the same problem with my '01 even though it's warm in Florida, not cold where you live. Like you, after the engine warms, it seems to go away. I have around 20,000 miles currently on the car, but can remember this always being a concern from the day I bought it. Initially, I thought I had a hung up lifter.

 

i bought my 01 new and when i first heard my "knock" itscared the hell out of me.you could hear it as ya pulled out in the cold morn.the ls motors being made of alum. have a bell effect on sound.i sold my coupe with 118 k on it.many runs down the strip with NOS.i sold it to a friend and she loves it,the bottom end is still untouched,now all this said ya still should get a second 'EAR' you may try o/30 oil for winter.ls motors are tough but they can and do lose a rod bearing

 

Strangely enough, you may trace this "knock" until warmed up to being the drive belt (idler bearing and/or a (non-stock) drive belt that is not quite in spec. My 2001 makes the same kind of (knock) sound and it goes away once everything is warmed up. I have not yet checked it out to be certain, but my87 Vette made a similar noise, and it was traced to the drive belt/idler bearing as the source.

 

I have a 2000 with 73k miles. Almost from the time it was new it had a knock when it was cold.
The dealer said it was piston slap and common with aluminum block LS1. It has got some worse but at 73K miles it doesn't use any more oil that it did with 0 miles, about 1/4 qt in 5000. I don't like the sound, especially when I ride in other C5s that don't knock but so far the car has been a very trouble free car. So, I guess I shouldn't "knock" (sic) it.