Cold Engine Knock
Thread Starter
2nd Gear
Joined: Oct 2005
Posts: 2
Likes: 0
Cold Engine Knock
I have a cold engine knock - any ideas please.
C5 Corvette.
2002 year.
13,000 miles on the clock.
Ok - This is what happens - - -
Start the cold engine.
Slight knocking sound.
Leave for about 2 minutes - then the noise goes.
For the rest of the day the engine sound is ok.
Its only when the engine is started from stone cold.
Thank you
Mark(England)
C5 Corvette.
2002 year.
13,000 miles on the clock.
Ok - This is what happens - - -
Start the cold engine.
Slight knocking sound.
Leave for about 2 minutes - then the noise goes.
For the rest of the day the engine sound is ok.
Its only when the engine is started from stone cold.
Thank you
Mark(England)
Burning Brakes
Joined: Jan 2004
Posts: 896
Likes: 1
From: Overland Park KS
A lot of others have this issue, often called "Piston Slap". Do a search here on the forum for "Piston Slap" and you'll find tons of articles discussing this. A lot of our cars have it. While it's annoying, it doesn't really cause any issues other than an annoyance. Just let it warm up before you beat on it and you should be good to go! BTW, my car has the same issue and runs like a rocket, even after 30k miles with Piston Slap during cold starts. 
Melting Slicks
Joined: Dec 2004
Posts: 2,322
Likes: 2
From: New York NY
Cruise-In VI Veteran
St. Jude Donor '05
i would try a bottle of chevron techtron fuel system cleaner first. pour it into the gas tank right before you fill up an almost empty tank. no oil change necessary. try that for starters.
Pro
Joined: Jun 2000
Posts: 662
Likes: 4
From: Germantown Tennessee
FWIW, I don't think the piston slap is a fuel issue. I have the slap problem and also use Techron regularly and the slap doesn't diminish.
Melting Slicks
Joined: Dec 2004
Posts: 2,322
Likes: 2
From: New York NY
Cruise-In VI Veteran
St. Jude Donor '05
i dont know, just going by its what it is advertised to do. reduce deposits related to knocking, etc. for 6 bucks i would give it a shot regardless of the outcome.
Le Mans Master
Joined: Dec 2000
Posts: 9,891
Likes: 1,829
From: Hot Springs AR
BTW, mine's had piston slap since I first owned her, nary a problem.
HTH, and have a good one,
Mike
Melting Slicks
Joined: Dec 2004
Posts: 2,322
Likes: 2
From: New York NY
Cruise-In VI Veteran
St. Jude Donor '05
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Burning Brakes
Joined: Sep 2006
Posts: 985
Likes: 0
From: Cumming Georgia
A lot of others have this issue, often called "Piston Slap". Do a search here on the forum for "Piston Slap" and you'll find tons of articles discussing this. A lot of our cars have it. While it's annoying, it doesn't really cause any issues other than an annoyance. Just let it warm up before you beat on it and you should be good to go! BTW, my car has the same issue and runs like a rocket, even after 30k miles with Piston Slap during cold starts.
The piston slap really grates on my nerves, but it doesn't seem to hurt the car. I just turn the radio up louder. Someday I might be able to afford an LS2 transplant, but until then I figure on just dealing with it.
Tim Glover
Thread Starter
2nd Gear
Joined: Oct 2005
Posts: 2
Likes: 0
The Knock.
When I first start the engine - there is a small knock.
"Its when I put it in drive" - the knocking is much loader.
After a couple of minutes the knock stops.
Could this still be Piston Slap.
Thank you all for your help.
Mark.
When I first start the engine - there is a small knock.
"Its when I put it in drive" - the knocking is much loader.
After a couple of minutes the knock stops.
Could this still be Piston Slap.
Thank you all for your help.
Mark.
2003 LS1 C5 same noise 4800 miles on it. No problems..2004 Silverado 4x4 same deal, 13,000 miles on it...ya I know; I don't drive them very much.
Tech Contributor
Joined: Dec 2006
Posts: 10,962
Likes: 29
From: Van Buren Arkansas
Wounded Warrior Escort '11
Knocking or tapping? If its coming from the top of the engine then its the lifters and if from the bottom, its piston slap or worse, rod bearings. I've done the lifter thing on my '99 two and a half years ago now. Had one lifter at a minimum that was bleeding down when cold. It would tap when I started it up(cold) and initially would only last a few seconds. Then it slowly got worse and worse. Near the end, it would tap till the engine temperature actually started to warm up and then suddenly it became louder and wouldn't go away unless a load was placed on the engine and so on. Replaced the lifters, all was happy and quiet once again.
Burning Brakes
Joined: May 2006
Posts: 816
Likes: 0
From: Georgetown Indiana
Its seems like mine has been worse lately or I may just be listening harder. If I turn the car off and then start it 5 minutes later it will do it all over again, untill it is ran for about a 1/4 mile. It seems to do it if I take off from a dead stop at a slow speed.
Tech Contributor
Joined: Dec 2006
Posts: 10,962
Likes: 29
From: Van Buren Arkansas
Wounded Warrior Escort '11
You might want to look at your oil pressure when you restart and the engine is warm. Might have a problem developing there.
