RacerX

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by JNorris:
<strong>Unfortunately the noise does not go away after the car is warmed up, just the tone/pitch changes.
</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Mine is noisy all the time too. I've put about 500 miles on it since the noise started and it dosn't seem to have gotton worse. Has yours?

JNorris

iTrader: (4)

The noise became louder after I switched to synthetic oil. I have now switched back to dyno oil and the noise is not as bad. There are times when there is no noise at all and other times it is there. The noise does not seem to be getting louder. The noise does go away after I rev the engine past 2000 rpm then will slowly return. Listen to the SOUND CLIP (1.3mb) below to hear what I am talking about.

Turn up your volume to hear it well.

Revving sound clip

RacerX

That is exactly what mine sounds like. I'm checking my rod bearings for wear before I get on it hard again.

<small>[ May 03, 2002, 09:30 PM: Message edited by: RacerX ]</small>

patSS/00

iTrader: (6)

Rumor has it (from LS1.com) that there will be a service bulletin out this month for piston slap.

DaddySS

I agree with a bad case of piston slap.

RacerX

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by patSS/00:
<strong>Rumor has it (from LS1.com) that there will be a service bulletin out this month for piston slap.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">So will that help me if I'm out of the 36k mile warranty?

patSS/00

iTrader: (6)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by RacerX:
<strong> </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by patSS/00:
<strong>Rumor has it (from LS1.com) that there will be a service bulletin out this month for piston slap.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">So will that help me if I'm out of the 36k mile warranty?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">No idea - like I said it's just a rumor. There've been a huge number of posts about piston slap (or cold knock, whatever you want to call it) on LS1.com - do a search there to read all about it. It's pretty common. My car has it, I'm trying to figure out what to do about it (if anything) while I've still got a year left on warranty. Seems like the key thing is to figure out if you've got an overbored cylinder, or if it's "normal" piston slap. Wish I knew how to find out, without tearing down the engine.

16again

iTrader: (1)

I have a 2001 Corvette. Just turned 20,000 miles two weeks ago and suddenly that noise is part of my start up when cold as well. I have been told it may be piston slap, lifters, or rocker arms. Don't know what it is but it's frustrating as heck to hear that on a $45,000 car! My car never goes to the dealer so I will probrably start with the easy stuff like replacing the roller rockers this week. Hopefully thats what it is.

Bob

BADZ

iTrader: (5)

PISTON SLAP IT IS!!!!

A bunch of motors have been returned and pulled out under warranty because of this tapping like sound!!!!

JNorris

iTrader: (4)

WOW! It seems that the overwhelming opinion is that it is piston slap.
The noise is coming from the front of the motor behind and below the water pump. Are cylinders 1 and 2 more likely to have piston slap than the other cylinders?

What test / check can be performed to confirm the problem is piston slap?

Thanks

John

JNorris

iTrader: (4)

Well I took off the ASP pulley and cranked up the car. After about 2 minutes the knocking/slapping came back. So it was not the pulley. <img border="0" title="" alt="[Sad]" src="gr_sad.gif" />

I also did some more troubleshooting. With the engine running I pulled off the coil wire to #1 and the noise became very quiet if not totally gone. I went ahead and put #1 back on and the noise came back after about 1 min. I then pulled #3 and then #2 and there was very little change in the knocking/slapping sound.

What is this an indication of?

<img border="0" alt="[guns]" title="" src="graemlins/gr_guns.gif" /> 98 Z28 with knocking/slapping sound coming from the engine.

Thanks

John

2001SS#3013

iTrader: (2)

If this were to turn into a service bulletin, how would GM go about fixing the problem? Does anyone have a clue.

SIKLS1

I have the same sound, i put it down to a lazy lifter not pumping up, it keep's bleeding off, i see if this is cover under warranty ?.