brandon_01_ta

what is that knocking sound?? bought the car less than a year ago and it didnt make that sound when i bought if i've only put about 3k miles on it... i did an oil change right after i got it and ever since then it has made the knocking sound... i used castrol syntec 5w40 the first time and it has penzoil platinum 10w30 in it now.... is this piston slap or what? thanks..

http://www.youtube.com/watch?v=PGbt12sYe5g

SOMbitch

iTrader: (8)

I have a 5.3 piston slap motor in my Z-71 and that definitely is not PS. If it is in the topend it could be one of many things but if it is in the bottom I would bet rod knock.

Try to isolate where it's coming from and post up again......

nhraracer

iTrader: (6)

Does the sound go up and down with the engine or does it stay the same

brandon_01_ta

it goes up and down with the engine

nhraracer

iTrader: (6)

Could be a warped lifter. Like the previous poster depends where the noise is coming from. I thought I had a bad lifter but never honed in on it and it was the water pump

BadgeZ28

iTrader: (28)

Take your accessory drive belt off and see if it goes away. My Power Steering pump makes a similar noise. I call it a clacking type noise. Oh, just a reminder, don't run it very long without the belt.

RevGTO

iTrader: (12)

Does it improve after the car warms up? My buddy's WS6 has a really loud knock like yours when cold (think it's a lifter, not ps) but it gets better when the car gets hot.

It doesn't seem to have any ill effect - his car screams.

kdick91

iTrader: (1)

I have the same noise. Only I also have an exhaust leak, but I'm taking care of the pretty soon. Check for leaks, but alot of the LS1's have noisy valvetrains. But when you said that it appeared... Idk, rules out alot. But I wouldn't sweat it if it runs fine. I've had it forever and it sounds identical to yours.

brandon_01_ta

yeah it seems to quieten down some after it warms up... but yeah it runs fine, doesnt seem to be effecting performance at all.. but idk

brandon_01_ta

don't think it's an exhaust leak but i could be wrong... the main reason is because when i bought the car it did not make that noise... about three days after buying it i did an oil change and used castrol syntec 5w40 european blend and it has knocked ever since then

99blancoSS

iTrader: (115)

need better audio . pop the hood and get close to the heads. first one side then the other. try and narrow down drivers side or passenger side. Then narrow down top or bottom.

I had a vicious knock once, most thought it was a rod but it turned out to be the substrate in the hi flow cat had come apart and was raping and the sound was resonating through the pipes.

RevGTO

iTrader: (12)

These LS1 motors tend to be noisy. Noises that would set off alarm bells on most other motors are common on these. It's tough to adjust to, but noisy as they may be, they keep running - and running hard - in spite of the noise.

How many miles on the car? I've noticed more and more noise develop as my A4 car gets close to 80k. And my M6 car, which is at 84k, is just plain noisy.

90TSiAWD

Sounds just like my car, mine started doing it after I put RP in it all it is, is lifter tick mine has basically went away after I switched to a conventional oil GC 10-40.

But I would get a better video with the hood up and you revving as stated above.

fr500c

Sounds like my car, the noise is a bit worst when the engine is under load and the noise seems to appear a few seconds after I start the engine...

92SilverSHO

iTrader: (3)

I have the same noise. Always had since i bought my car. Thats 5 years later no problem. I think its slap, but you only notice it at idle. It doesnt go up with the revs though. I use Castrol 0w-30.

98blackbirdta

iTrader: (7)

i have the same sound

justout4u

iTrader: (3)

if it goes away after two minutes of running and doesnt go up with rpm id say its the normal piston slap.

99RTA

iTrader: (-1)

My 02 Formula has the EXACT same noise. I'm sure its a lifter or lifters. Mine also has terrible lifter noise at start up and after a restart hot for a few seconds. I have good oil pressure too, Always above 40 even at idle.

brians91formula

iTrader: (12)

I changed to GC 0w30 and I got the same noise but not as loud. I then switchted to Pennzoil Platnium 10w30 and it went away..... hrm??

camarosam22

Mines the same way when I first start it up, but not that loud. I put more oil in it and it did hush it a little.