SuthernFlames316

What is piston slap and how do u know if you have it? I have a 99 5.3.

cstchevy

you will here a loud clunks usually on start up. Like the piston is hitting the head or something like that.

shandy294

It's a cold start thing....loud clatter for a short time until the pistons expand. Not all do it...most prevalent in 99 and 00...I have a 04 4.8 and it doesn't do it and according to a guy on this site,it never will.
A guy here at work has a 04 SS Silverado (6 liter) that does...I heard him start it as he was going home.

cstchevy

if you have it and didn't know about it when you start it up it will scare the hell out of you thinking something is seriously wrong.

zippy

if you're a lakers fan, you know you have been there...

seriously, if you own a gm engine including 2.2, 3.1, 3.4, 4.6, 4.8, 5.3, 5.7, 6.0, 7.4, or 8.1, you probably have heard it.

CARAZYCUTER 4.8

piston slap is the result of gm engineers designing the new gen III motors with no piston skirts to lower rotating mass. The skirt is the part of the piston that is on the bottom end that is larger than the top end. Once the vehicle heats up to a certain temp the top part of the piston expands enough to keep the piston from moving around in the cylinder here is a copy of two gm bullitens that gm released. I have to sit down with 3-5 customers a week in my office explaining that this is normal. It is more prevalant in the 6.0 lq4 & lq9 & ls1 with 6-speed
Info - Engine Knock on Cold Start #01-06-01-022 - (08/22/2001)
Information on Engine Knock on Cold Start
2001-2002 Chevrolet and GMC C/K Pickup and Utility Models

with 6.0L Engine (VIN U -- RPO LQ4)

Some of the above vehicles may exhibit an engine knock noise that begins in the first several thousand miles/kilometers of use. The knock noise is most often noticed during initial start-up and typically disappears as the engine warms up. The noise is usually more noticeable on the initial start-up when the temperature is below 10°C (50°F) or if the vehicle has not been used for several days.

This noise may be caused by an interaction between the piston and the cylinder wall. GM Powertrain Engineering, and an analysis of engines returned with this condition, has confirmed that the noise is not detrimental to the performance, reliability or durability of the engine. The noise does not have any effect on the longevity of any of the engine components.

[B]Important
At this time, replacing the engine assembly or pistons will not eliminate this noise.
Please share the information found in this bulletin with customers who inquire about this condition. In the event they have additional questions or concerns, please advise them to contact Customer Assistance at the numbers listed below for further information.
Number
Deaf, Hearing Impaired, or Speech Impaired*

Chevrolet
1-800-222-1020

8a.m. - 11p.m. (EST)
1-800-833-2438

8a.m. - 11p.m. (EST)

GMC
1-800-462-8782

8a.m. - 11p.m. (EST)
1-800-462-8583

8a.m. - 11p.m. (EST)

Canada
1-800-263-3777

(English)

1-800-263-7854

(French)

7:30a.m. - 11:30p.m. (EST) (Mon-Fri)

7:30a.m. - 6p.m. (EST) (Sat)
1-800-263-3830

7:30a.m. - 11:30p.m. (EST) (Mon-Fri)

7:30a.m. - 6p.m. (EST) (Sat)

* Utilizes Telecommunication Devices for the Deaf/Text Telephones (TDD/TTY)

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION
----------------------------------------------------------------------------------------------------------------------------------------------------

© Copyright General Motors Corporation. All Rights Reserved.
Info - Engine Knock on Cold Start #01-06-01-028A - (03/18/2003)
Engine Knock on Cold Start
1999-2002 Chevrolet and GMC C/K Pickup and Utility Models

2002 Cadillac Escalade (2WD)

with 4.8L, 5.3L or 6.0L Engine (VINs V, T, Z, U -- RPOs LR4, LM7, L59, LQ4)

This bulletin is being revised to add an additional engine to the models section. Please discard Corporate Bulletin Number 01-06-01-028 (Section 06-Engine).

Some of the above vehicles may exhibit an engine knock noise that begins in the first 19,000-24,000 km (12,000-15,000 mi) of use. The knock noise is most often noticed during initial start-up and typically disappears within the first 5-30 seconds (may last longer in extreme cold temperatures). The noise is usually more noticeable on the initial start-up when the temperature is below 10°C (50°F) and may be more pronounced on the first cold start following a long trip.

This noise may be caused by an interaction between carbon that has formed on the piston, the piston motion and the cylinder wall. GM Powertrain Engineering, and an analysis of engines with this condition, has confirmed that the noise is not detrimental to the performance, reliability or durability of the engine. THIS NOISE DOES NOT HAVE ANY EFFECT ON THE LONGEVITY OF ANY OF THE ENGINE COMPONENTS.


Important
At this time, attempts to repair this condition by replacing the engine assembly or pistons are not recommended.


Please share the information found in this bulletin with customers who inquire about this condition. In the event they have additional questions or concerns, please advise your Area Service Manager.



GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION


© Copyright General Motors Corporation. All Rights Reserved.


--------------------------------------------------------------------------------
Document ID# 1271016
2002 Chevrolet Chevy C Silverado - 2WD


--------------------------------------------------------------------------------

FILE

iTrader: (5)

Guys watch it.. There is one member in here who is very sensitive about this issue. He will argue that these truck don't have an engine noise problem to the end.

shandy294

Anything other than rings-to-wall contact cannot be good,right?

zippy

i don't actually see a problem with the piston slap, just that it's there.

GroundControl

Imagine your crankshaft spinning, with the rods and pistons doing their thing... as the piston starts to go upward(from BDC), the rod is angled like this .... / ... then as the piston reaches top dead center it is straight up ... I .... then as the piston moves down, it angles the other way ... \ ...

Before the engine is warm, the piston has not expanded, so it is a little bit smaller than the bore of the cylinder, so when the piston "rocks" or changes from leaning to the left to leaning to the right (this happens at TDC) it SLAPS the side of the cylinder. Once the piston expands, it fits tighter against the cylinder walls, and stops slapping.