my Trailblazer (2002, 32.000kms) developed a kind of deep-sounding, distict
knocking that seems to come right out of the bottom of the engine. No
metallic 'pinging', more like a thumping. It can be best heard when I listen
at the right front wheel-house just after starting the engine. It becomes
quicker when I rev up the engine. It's even more distict during cold
weather. After a minute or so, it just fades away. I use the best gas
available. My dealer says everything is just fine. I am not so sure. The car
is still on warranty. What makes the thing worse is that here in Germany
nobody has the faintest knowledge about this car. Any help by you
It's called Piston Slap and is very common with the newer GM engines
(especially the 8-cylinders). While annoying, it's nothing to worry about.
Do a yahoo or google search for "Piston Slap" and have fun reading the
kajillion results you get! Thisissue isn't just with GM, but also with Ford
and Toyota products.
Thanks for helping me, Doc. I did not know that the 6-Zyl inline engines
could get piston slap too. I always thought that this was an issue of the 8
cylinder motors. But I never stop learning (:-;
Actually, you didn't goof, Doc. The 4.2 does exhibit
the piston slap noise that all the 3100/3400 and the
newer small blocks do. They all seem to be noisy for
the first few minutes of operation, but for whatever reason,
nobody seems to complain about it. But it is there. I
hear it everytime I drive them in off the lot.
In the case of this posters vehicle, he may just be
hearing the normal noise they all make, but he should
be getting a new engine because of the cracking sleeve
syndrome. Eventually, it will break.
There is a problem with "some" 2002 Trailblazers. The cylinder
liner can crack and cause extensive engine damage. GM actually
has a "special policy" out on this.....and if your vehicle falls within
certain VIN break points, they will install a new engine, once they
have verified the problem. For your vehicle, the VIN breakpoints
are from 22100007 to 22358861. Check and see if your vehicle
VIN falls within that number range. I'll include the particulars of
the special policy below.
Special Policy Adjustment - 4.2L (LL8) Bore Liner Cracking #03019 -
03019 - Special Policy Adjustment - 4.2L (LL8) Bore Liner Cracking
Certain 2002 Chevrolet TrailBlazer; GMC Envoy; and Oldsmobile Bravada
Some customers of 2002 Chevrolet TrailBlazer, GMC Envoy and Oldsmobile
Bravada with 4.2L (LL8) L6 engine produced during the 2001 calendar year may
experience cracking of an engine cylinder bore liner, resulting in engine
noise, poor performance, and/or stalls with no engine re-start. Engine
replacement is necessary to correct this failure.
Special Policy Adjustment
This special policy covers the condition described above for a period of
seven (7) years or 100,000 miles (160,000 km), whichever occurs first, from
the date the vehicle was originally placed in service, regardless of
ownership. The repairs will be made at no charge to the customer.
For vehicles covered by Vehicle Service Contracts, all eligible claims with
repair orders on or after June 13, 2003, are covered by this special policy
and must be submitted using the labor operation codes provided with this
bulletin. Claims with repair orders prior to June 13, 2003 must be submitted
to the Service Contract provider.
Involved are certain 2002 Chevrolet TrailBlazer, GMC Envoy and Oldsmobile
Bravada model vehicles equipped with 4.2L (RPO LL8) L6 engine and built
within the following VIN breakpoints:
Bingo! It does.
But I didn't notice any loss of power so far. Do the engines fail completey?
When does this occur and how do I know when it's going to happen? I am not a
"soft" driver and I like to travel at high speeds on the autobahn. Does this
I know, it's a lot of questions, but I like my Trailblazer and would like to
keep it for a while.
Thanks a lot for helping me.
After re-reading your original post, all that you may be hearing
"at this point" is the normal piston noise that these engines make
when cold. But, you do have the defective engine in that vehicle,
and it should be replaced. I suspect that you may have to jump
through some hoops to get the updated 2003 engine, but that's
what you should be shooting for. To date, we've only seen one
failure in our dealership, but I've heard from other GM techs around
the city, that numerous engines have failed and been replaced.
It's usually catastrophic when it does happen.
Take the number of the special policy that I quoted into your
dealership service manager and sit down and talk with him about
it. GM does cover the motors from failure for a long time, but
I'd be trying to get a motor sooner then later.
If they do replace the motor, it's important that they follow the
directions and switch over the oil pan, spark plugs, and knock
sensors from your engine. The 2003 engine does not use an
oil level sensor like your engine, and the other two items are
probably due to some calibration issues.
Ian (and, of course, all the others), thank you very much for your
Does this mean my dealer will have to change my engine even it has not yet
Or do I have to wait till the pistons come shooting out? I do not want this
to happen when I'm hundreds of kilometers away from my dealer. I often have
to travel long distances and Chevy dealers are a rare breed in Europe.
Upon reading the special policy closer, it looks like you have to
wait until the failure happens. It does say "engine noise" so that's
where I would start. Complain about the engine noise, (which
you've already done) and then bring this special policy to their
GM should have sent you a letter about this special policy.
Are you the original owner? If not, you may not get the
letter. This is a small section of what they say in there.
What We Have Done
To address the above mentioned condition, General Motors is providing owners
with special warranty coverage. If this condition occurs on your 2002
Chevrolet TrailBlazer, GMC Envoy or Oldsmobile Bravada within seven (7)
years of the date your vehicle was originally placed in service or 100,000
miles (160,000 km), whichever occurs first, the condition will be repaired
for you at no charge .
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