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Thread: 2000 Silverado - "Piston Slap"

  1. #1
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    2000 Silverado - "Piston Slap"

    I have a 2000 Silverado Z71 with the 5.3l engine. In the morning when I first start it up I get a very loud knocking noise in the engine for about 30-60 seconds. I thought it was a valve problem. I took it to my local Chevy dealer and they said the noise is called "piston slap" where the skirt of the piston is hitting the cylinder wall until it expands enough. They said that they have contacted Chevy about this and were told it is normal.

    As far as I can see, this noise is not normal. No engine should make this type of noise for any period of time. It sounds like the engine is tearing itself up. How can that be "normal".

    Has anybody else experienced this problem? Is it a problem? My warranty runs out soon and I'd like to get it cleared up before thast time, but I need ammunition to push them into a repair.

    Any info would be greatly appreciated.

  2. #2
    Senior Member++ DodgeChick's Avatar
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    You're right...thats not "normal" its just that its not major engine failure so they dont want to replace anything. I would insist they fix it...and tell them Im under warantee and that is not "normal".

    What is it with dealerships and lousy business lately?
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  3. #3
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    I found a lot of tech bullitins on www.alldata.com, but they want $24.95 to view them. Is there a source for these bulletins online for free? I'd like to take it with me when I go to see them again. The bulletin that addresses this is:

    01-06-01-028A MAR 03 Engine - Knocking on Cold Start Explanation

  4. #4
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    dont worry it isnt going to hurt a thing the LT1s were famous for this. and it is normal because of the design of the piston they used the skirt will hit the walls until it exapnds. nothing it wrong.

  5. #5
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    I was able to get a copy of that tech bulletin from a local garage that subribes to the service. It basically says that the noise is caused by Carbon buildup on the piston skirt that impacts the cylinder wall. It also says that this does not pose a risk of engine failure and that changing the pistons would not correct the issue.

    I guess I feel a little better, but after investing thousands into a vehicle it would be nice to start it in the morning and not have to listen to an engine that sounds like its coming apart. I would have thought that if this has been an issue since 1999, GM would have done something about it by now.

  6. #6
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    Check this site for some info: www.pistonslap.com

  7. #7
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    if its a carbon build up thare is an easy solution. take off the air filter and keep the motor at about 2300 rpm and dump a large glass of water in it. dont worry the compression of the engine will push it out. there will be a big cloud of white. thats because air steam mixture. total time to dump the water should be about 4 seconds. i work on aircraft motors in fort wayne. ive done it on my truck several times it works. seriously!

  8. #8
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    sounds like that could crack the head if enough water got into one of the cylinders.

  9. #9
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    i have a 98 silverado z71, also a 350. i have a problem with piston slap also. it truly is no problem. i work on large engines and ive noticed that on older models chevy put a lubricant of some sort between the piston and the cylinder. over time this lubricant wears away and you get a space between the piston and cylinder. like dealer said, it will go away once it expands to fill the void previouslly occupied by the lubricant. I fixed it but thats only because it bothered me. it doesnt harm the piston or cylinder at all.

  10. #10
    Senior Member 72'CaminoKid's Avatar
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    my 5.7 and my dad's 4.3 both do the same thing, only in cold weather.... we were thinkin it was a lifter. i'm gonna change my oil this weekend though ( been a little over 3 months since last did it) and i'll just see if that makes a difference. but i agree, the noise just makes my insides turn, it sounds like my engine is practicing self-mutilation
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