Dreaded piston slap (maybe)!!
Thread Starter
Drifting
Joined: May 2003
Posts: 1,755
Likes: 97
From: Sandy Utah
Dreaded piston slap (maybe)!!
Now that the cold weather is here (10 F this morning), my '01 coupe is clattering on cold startup. It is noisy at idle and gets worse up to approx 1500 rpm when it quits entirely. I have done a search hoping to find a thread that I remember attributed this as piston slap and that sometimes, carbon buildup can be the culprit. Has anyone been able to "cure" the rattle by running at high rpm over an extended time (say 20 mins @4 grand) to clean the carbon out of the combustion area. Obviously, the 20 min run was done under load on the road. Anyone with info? 
Instructor
Joined: Mar 2002
Posts: 165
Likes: 0
From: Apex NC
I am not an expert by any means, but it is my impression that all the C5 engines experience some piston slap until the engine is up to speed. Has to do with the physics of metals and hot and cold. The colder the weather, the more the metal contracts. The piston is incapable of completely filling the cylinder until it gets up to temp and expands and therefore slaps the cylinder wall. Nothing you can do but warm up the engine. Seems to me that running it at high revs until it heats up could do more harm than good.
I have a 2003 Z06 and never notice the slap until it gets colder like it is now. I let it sit for several minutes at idle by the time I am out of the neighborhood, all is well
I have a 2003 Z06 and never notice the slap until it gets colder like it is now. I let it sit for several minutes at idle by the time I am out of the neighborhood, all is well
Race Director
Joined: Apr 2001
Posts: 19,329
Likes: 15
From: Saint Augustine, FL
Mid-TN Events Coordinator
St. Jude Donor '03-'04-'05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15-'16
Piston slap, and 'knocking' from carbon build up are two different things. Per GM, piston slap is normal. Everything you described sounds exactly like what I had on my 1996 S10 pickup. It started doing it after about 10K miles. My Vette on the other hand has never done it.
If you're truly concerned about carbon buildup, go purchase Sea Foam, or the GM stuff and do it the right way. Just make sure you change your oil afterwards.
If you're truly concerned about carbon buildup, go purchase Sea Foam, or the GM stuff and do it the right way. Just make sure you change your oil afterwards.
Racer
Joined: Jun 2005
Posts: 333
Likes: 1
From: Mendota Heights MN
My 99 "hammered" like he!! when cold. I took it to the dealer, and was diagnosed with "lifter" noise. They pulled the heads and installed a " lifter kit" under warranty.
No more noise.
I have suspected this problem is known by GM, but only corrected when someone complains.
No more noise.
I have suspected this problem is known by GM, but only corrected when someone complains.
Drifting
Joined: Jan 2005
Posts: 1,600
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From: Spring Hill, Florida Life is all about new beginnings;...TRY ONE!
St. Jude Donor '07-'08
For what it's worth, Someone mentioned a while back that th K&N oil filter (Gold?) helped with that somewhat, I don't know why though...... 
I thought I might try it on my '01 the next oil change.
I thought I might try it on my '01 the next oil change.
Thread Starter
Drifting
Joined: May 2003
Posts: 1,755
Likes: 97
From: Sandy Utah
Thought that I would try the "high rpm tuneup". Took the car out west of Salt Lake where the state road is straight and deserted (mostly) and I could run for several miles at a time at high speed/high rpm. I have an A4 with 3.15 so 4 grand was an even 100 mph and when I took it up to 5 grand, the speed was an even 125 mph all in third gear. I made several runs and brought the car home to sit overnight in the cold. This morning, when I started it up, the clatter was barely noticeable at idle and was completly gone at 1500 rpm. This is a fair weather driver and most of the mileage (17,000) is done around town at less than 2000 rpm. Maybe the engine just needed to be "cleaned out". I hope that this is a permanent fix since I do not want my dealer to go into the engine.
Race Director
Joined: Jul 2005
Posts: 11,308
Likes: 1
From: The Beautiful Greater Bay Area California
Originally Posted by JR_VETTE
Piston slap, and 'knocking' from carbon build up are two different things. Per GM, piston slap is normal. Everything you described sounds exactly like what I had on my 1996 S10 pickup. It started doing it after about 10K miles. My Vette on the other hand has never done it.
If you're truly concerned about carbon buildup, go purchase Sea Foam, or the GM stuff and do it the right way. Just make sure you change your oil afterwards.
If you're truly concerned about carbon buildup, go purchase Sea Foam, or the GM stuff and do it the right way. Just make sure you change your oil afterwards.
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Melting Slicks
Joined: Jun 2004
Posts: 3,439
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From: Newark, DE
St. Jude Donor '06
Originally Posted by RatedX
Someone mentioned a while back that th K&N oil filter (Gold?) helped with that somewhat, I don't know why though......
I'm sure many people have used them w/o incident, but I would be uneasy having the lowest spot on my car be something as vital as part of the engine lubrication system.
Baldwin B31s have similar flow characteristics, but without the nut. I use them exclusively.
