Engine knock help
Le Mans Master
Joined: Feb 1999
Posts: 6,269
Likes: 1
From: Richmond Ca
Originally Posted by vettekid85
When I cold start my car I have a slight engine knock. Its very noticable at first, but after I drive it for a minute it goes away. Is this normal or is there something I can do?
http://www.pistonslap.com/
Le Mans Master
Joined: Feb 1999
Posts: 6,269
Likes: 1
From: Richmond Ca
Originally Posted by vettekid85
No its not piston slap. Its a lower pitch and it goes away after a minute. Any other ideas
http://forums.corvetteforum.com/show...lap&forum_id=1
Cruising
Joined: Nov 2005
Posts: 11
Likes: 0
From: Charleston WV
I had an 02 C5 with 1800 miles that the factory over bored 5 cylinders on. It was like pulling teeth to get GM to address this. When they figured out that I wasn't going away they wanted to replace the pistons in the over bored cylinders with "special cast pistons to fit the over bored cylinders" In other words 3 pistons of one size and 5 of another. That didn't happen. To make a long story short as far as piston slap goes mine sounded worse the warmer it got.
Race Director
Joined: May 2000
Posts: 14,542
Likes: 5
On vehicles built in the last decade, piston slap that occurs for a few seconds on cold start is quite normal. My own vehicle, with only 20,000 miles on it has piston slap for about 5 seconds when first started on a below freezing winter morning. Service information from General Motors states "A cold Piston knock which disappears in 1.5 minutes should be considered acceptable". From experience, I have found that piston slap that occurs only during cold starts and lasts only for a minute or less causes no problems. Just don't place a load on the engine until the pistons have expanded and the clearance has been reduced.
http://www.canadiandriver.com/articles/jk/020320.htm
http://www.canadiandriver.com/articles/jk/020320.htm
