Latest GM TSB including 2012 models!
Around 1998, GM switched from a
"Select Build" method of manufacturing and/or assembling engines to
a "Net Build" method, in order to save money on manufacturing and/or
assembly. In the Select Build process, pistons and cylinders are
matched for size and fit. GM's new "Net Build" method of
manufacturing and/or assembly, in contrast, assumes all pistons will
fit equally well in all cylinders and does not allow for variations
in the size of engine cylinders or pistons. The pistons of slightly
varying size (all within spec) are not individually matched with the
cylinders of slightly varying size (all within spec).
Excessive “piston slap” occurs because an automobile manufacturer
(GM) designs and/or manufactures a defective engine in which the
clearance between the piston and cylinder bore is too great.
Essentially, the piston moves sideways and “slaps” or “knocks” hard
against the cylinder bore and causes damage to the engine pistons
and cylinders, excessive smoke emissions, excessive oil consumption,
carbon buildup on piston heads, decreased mileage, and a loud and
obnoxious “slapping” or “knocking” noise, all of which diminishes
vehicle resale value in the trade.
knocking engine could lower the value
of a vehicle by $4,000 to $6,000 at trade-in"
Charlie Vogelheim, executive editor for Kelley Blue Book
Detroit Free Press
"The very evidence provided by the manufacturer
(GM) to indicate this condition is not a problem
demonstrates that it is a problem."
2012's with piston slap!
GM Consumers, do you have
a 1999-???? GM
engine that displays any of the following problems?
A loud embarrassing and annoying internal engine knock.
Many are defective due to design and manufacturing quality
piston slap here.
of wear related materials in oil analysis samples performed
by independent laboratories.
Vertical piston and cylinder wall scuffing/scratching or
scoring on the hammering (noisy) cylinders upon visual
See photos here.
combustion chamber compression on the hammering (noisy)
Did GM or there agents tell you
they would fix your defective vehicle in writing/and/or
verbally when the phantom
"New Piston" fix WAS TO arrive in
the spring or summer of 2002? GM did in fact admit
it had a problem and that its engineering department was
working on the fix. The fix was promised to be made to
consumer’s engines in the spring or summer of 2002. As the
number of slapping engines grew and the cost to repair them
grew as well,
GM changed its policy.
We are receiving complaints from fellow slappers
who are taking their vehicle's into dealerships
for piston slap. Apparently some dealerships are saying it is
not giving the consumer a work order, even when
asked to do so. If this happens to you be sure to
keep the following information for your records:
1. Date of repair attempt
2. Time of repair attempt
3. Service writer/managers name**
4. Name of person refusing work order**
5. Service tech's name refusing to do work**
6. Any other items/notes/observations to show proof you were there
** - Write down names in front of the person.