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Old 12-14-2010, 01:55 PM   #1
mdixon
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Default Engine knock when cold?

When my 2000 Vette is cold like in the morning it knocks a little. What causes this?
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Old 12-14-2010, 02:08 PM   #2
tblu92
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This is commom in SOME LS engines-- if it sounds like an engine rattle and not a pinging noise---
It's known as a "piston slap"--GM has acknowledged this issue and says there is no fix and it won't affect the engine performance or life--
BUT I always let the eng warm up til it disappears before proceding just to be safe
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Old 12-14-2010, 05:33 PM   #3
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I had piston slap when cold on a few ls1 f bodys a 98 TA with 80k and a 00 Z28 with 70k, my 00 vette does not have it 70k (yet...)
+1 on letting them warm up.

My dad still has the 2000 camaro and it has over 100k now and runs great.
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Old 12-14-2010, 05:56 PM   #4
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my 2000 has piston slap in anything colder than 35 or so. It goes away after about 100 feet.
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Old 12-14-2010, 07:35 PM   #5
C5XTASY
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Quote:
Originally Posted by C.Davis View Post
I had piston slap when cold on a few ls1 f bodys a 98 TA with 80k and a 00 Z28 with 70k, my 00 vette does not have it 70k (yet...)
+1 on letting them warm up.

My dad still has the 2000 camaro and it has over 100k now and runs great.
+2 on the warmup.
Ed
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Old 12-14-2010, 09:07 PM   #6
docohm
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My 2001 does the same thing when it's below 40 here, goes away in a couple of blocks as it warms up. She has 80K miles now and still running great.
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Old 12-15-2010, 10:23 AM   #7
Marlin
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Yea my 01 with about 60k does it and my parents Z28 also has it and they are near/over? 200k on the factory motor.
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Old 12-15-2010, 10:54 AM   #8
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Most common problem is piston slap as was said. If the car is modded you may have a lean condition as the air gets denser when the temp drops. You could also have carbon buildup on the pistons causing detonation but that is most noticable when hot. Probably still worth doing a Seafoam treatment on it - can't hurt.
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Old 12-15-2010, 01:16 PM   #9
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Im gonn say its not piston slap. its cold as hell out and the oil is thick. takes some time to work it through. Thats just valvetrain noise without oil in it. Mine does the same in this cold. Its fine
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Old 12-19-2010, 04:01 AM   #10
rick4grafx
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Default What is "Seafoam" treatment

Quote:
Originally Posted by WKMCD View Post
Most common problem is piston slap as was said. If the car is modded you may have a lean condition as the air gets denser when the temp drops. You could also have carbon buildup on the pistons causing detonation but that is most noticable when hot. Probably still worth doing a Seafoam treatment on it - can't hurt.
What is "Seafoam" treatment
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Old 12-19-2010, 04:45 AM   #11
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My 2004 does it has 21000 miles. This is my third LS1 they all did it.
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Old 12-19-2010, 04:45 AM
 
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