Cold Engine Knock
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Joined: Jun 2000
Posts: 66
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From: Camp Hill PA
Cold Engine Knock
My 02 Z06 has a cold engine knock that I hear when I begin to engage the clutch or just touch the gas pedal after the clutch is fully engaged. I don't hear it at idle. The noise lasts about 7 minutes if I just idle and periodically engage the clutch to check for it.
1. Does anyone else have the same noise?
2. Has your dealer been able to diagnose what the noise is? My experience with 2 dealers is that they claim the noise is piston slap before they even listen to it. I'm not convinced, however, that they could differentiate one engine noise from another.
3. Has GM offered any compensation?
thanks
1. Does anyone else have the same noise?
2. Has your dealer been able to diagnose what the noise is? My experience with 2 dealers is that they claim the noise is piston slap before they even listen to it. I'm not convinced, however, that they could differentiate one engine noise from another.
3. Has GM offered any compensation?
thanks
Instructor
Joined: Feb 2002
Posts: 162
Likes: 0
From: C5 Land
Re: Cold Engine Knock (jeclarke)
Hi!
I have piston slap, and it sounds like a +100k miles mistreated engine when it´s cold!
If your sound is piston slap, it will be louder if you put the engine under light load.
Piston slapping occurs mostly when the engine is cold and under light load.
I have an -99 A4 with 1600 miles, and if i put it into D when the engine is cold it starts to knock quite loud.... :mad
My noice last about 2-3 minutes.
7 minutes seems much to me.
It´s pehaps something with the clutch in your case.
The noice in my car will also be worse when the engine oil quality is low (40% and less).
I think that a good way for your dealer to determine if it´s piston slap or not is to lift your car up and let the engine completly cool off (overnight),
stand under the car the next morning and start it.
I let my dealer do that last week, and now he is finally convinced!
The noice comes from cylinder 7 or 8, i have also read that it´s the most common on the LS1.
I don´t know what they will do about it, but something will be done since i have 2 years warranty left.
Do a search on the net for GM and piston slap, and you will find forums and sites made by people that have this problem.
Good luck!
(Sorry for my crappy english).
Jörgen.
[Modified by The Laplander, 11:49 AM 7/9/2002]
I have piston slap, and it sounds like a +100k miles mistreated engine when it´s cold!
If your sound is piston slap, it will be louder if you put the engine under light load.
Piston slapping occurs mostly when the engine is cold and under light load.
I have an -99 A4 with 1600 miles, and if i put it into D when the engine is cold it starts to knock quite loud.... :mad
My noice last about 2-3 minutes.
7 minutes seems much to me.
It´s pehaps something with the clutch in your case.
The noice in my car will also be worse when the engine oil quality is low (40% and less).
I think that a good way for your dealer to determine if it´s piston slap or not is to lift your car up and let the engine completly cool off (overnight),
stand under the car the next morning and start it.
I let my dealer do that last week, and now he is finally convinced!
The noice comes from cylinder 7 or 8, i have also read that it´s the most common on the LS1.
I don´t know what they will do about it, but something will be done since i have 2 years warranty left.
Do a search on the net for GM and piston slap, and you will find forums and sites made by people that have this problem.
Good luck!
(Sorry for my crappy english).
Jörgen.
[Modified by The Laplander, 11:49 AM 7/9/2002]
