"Cold Start Diagnosis"

[DenaliMCD]

it is not pinging, it is more like piston slap. High quality gas does not solve the problem.

[GMMerlin]

I don't get involved in "hot bed" issues on this forum.
I do try to give you as much information as I can to educate you and remove some doubt about the percieved "secret world" of the dealer.
The de-carbonizing procedure is a temporary customer satisfaction repair. It usually lasts about 15000 miles before the carbon build-up starts knocking again.
I have yet to see any vehicle with the cold knock come in for engine damage repairs. I have worked on many Gen III equipped trucks with over 250000 miles on the clock.
I also own an 02 GMC with a 5.3
here is the official word from GM.

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.

[jmarkmartin]

This is for everyone who has a 2000-04 Chevy/GMC/Cadillac Truck engine. I have had a noise in my engine that started as a tick sound and progressed into a knock. At times I wondered if I was going to throw a rod or something - it was awful! Long story short, I have searched the Internet and asked mechanics until I was blue in the face with frustration. I finally tried something a mechanic in Greenville, Texas suggested and it worked. Apparently Chevrolet has acknowledged a problem with carbon build up on the tops of the pistons. I know, this sounds like some hocus pocus load of crap, but read on. I went to the local Chevy dealership and bought 4 cans of "Top Engine Cleaner" (Chevy part number #105002 @ $6.54 a bottle). I then went home and removed all sparks plugs, used a funnel with rubber flex tube on the end to funnel the cleaner into each combustion chamber. I guess I put about 1 cup of this cleaner into each chamber. Man this stuff stinks to high heaven (warning label says "known to cause cancer in the state of California... good thing I don't live in California - joke). I then let it sit over night to disolve the carbon build up. FIRST THING - change the oil! The cleaner will seep down into the crank case. After I changed the oil I turned the engine over to force out the cleaner from the pistons (I should have stuffed the manifolds with towels to prevent the cleaner from going everywhere). I then put the spark plugs back in and turned it over. It took about 1 to 2 minutes to get the engine to start. Guess what? The knock/ping is gone. I mean it is completely 100% gone! There is no trace what so ever of a tick or noise at all. This process might or might not work for you, but I swear on my life this story to be true. I highly suggest you try this if you are experiencing the same engine noise.

[sTUNNA]

When you say the "clicking" sound, do you refer to the noises the engine makes after the car has been turned off, cause mine does that for maybe 5-10 minutes after I turn off the car. Or maybe Ive never realized it while driving. Mine makes a popping sound every 3 seconds.

[superdave885]

Originally Posted by sTUNNA

When you say the "clicking" sound, do you refer to the noises the engine makes after the car has been turned off, cause mine does that for maybe 5-10 minutes after I turn off the car. Or maybe Ive never realized it while driving. Mine makes a popping sound every 3 seconds.

that noise is the exhaust and catalytic convertor cooling down. metal cracks when it's expanding and contracting. completely normal, nothing can be done.


as for the "cold knock", i'm a GM technician, and i've seen this a hundred times, along with my own yukon. when gm designed the engine, they made the piston skirts shorter to save weight on the pistons. this made the pistons "cock sideways" in the cylinder and make the slap noise that you hear. actually, they only move about 2/1000ths of an inch, but enough to make noise. it does not hurt the pistons or cylinder wall at all. mine has been doing it since 25k miles and i'm now at 135k. not worse or anything.

the top engine cleaner does work temporarily, but only if it's dumped directly into the cylinder. not drawn through a vacuum port. the noise will come back.

hope this helps.

[maxwedge]

Welcome to AF, please look at the dates before posting this thread is dead, 4 yrs old, thanks.