"Cold Start Diagnosis"

See my original thread "'01 to "02 Yukon Denali". Anyway, I brought my Denali in to have a Cold Sart diagnosis done on the vehicle and the service rep. just called me back this morning and told me that I do have a knocking sound. Possibly a piston problem. I suggest ALL yukon owners to get this diagnosis done ASAP BEFORE their regular warranty expires, unless you have an extended warranty. The person that I met who had this same problem got a brand spanking new engine from GMC.

You may ask yourself why wouldn't this be a recall? IMHO it would cost too much money for GMC. If only a handful of people found out about this problem it wouldn't cost as much as a TOTAL RECALL! I'll keep everyone updated on this forum.

As I stated before this is not a problem with all Yukon's. My Yukon SLT has no such noise. So yes it might be wise to investigate...no this is not a recall. GMC would get sued if it were a true diagnosis on all vehicles.

Jon

I'm suprised your advisor didn't tell you the real story on this. If it is the normal piston slap noise that most of the Generation 3 engines have I bet you it goes away when warm. What causes this is a few differnt things. 1. The engine was designed with minimal piston skirts to achieve the performance that everyone is after. 2. Todays gas. 3. What actually causes the noise is carbon buildup on the piston surface and sides. I have seen pictures of engines with 200 and 300k on them that all have had documented noise concerns. GM had given these customers new engines just to see how they where doing and when torn down the cylinder walls still had crosshatches and the bearings where obviously worn but not spun. I know they had looked into teflon coating the piston skirts for newer vehicle's only for customer satisfaction.
I have personally taken 3 apart and cleaned the surface of the pistons to remedy this, it works great but only lasts about 15k. You may want to try going to your local parts store and look for a product that can clean this without tearing your engine apart. GM has a product called Top Engine Cleaner that does a damn good job of it. If you noise does go away when warm thats probably it, as they warm the carbon softens or decrystalizes and stops making noise.

I am looking for information. I have a 2001 Yukon that has what I would call a 'knocking' noise. Actually, it is more of a loud ticking sound. When the car was new, it only did it on a cold start. Now, with 34,000 miles on it, the noise is constant. The dealer says there is nothing wrong, "they all do that." My guess is that if they all did that, it would be listed as a feature of some sort.......

There are a couple 0f issues GM is looking at for possible areas of concern with the Gen III engines.
1. Needle bearings from the rocker arms coming apart and ending up in the oil pan.
2. Oil pump pickup tube O'ring splitting aerating the oil.
3. Piston issues from excessive carbon buildup on the ring-land sides.

Most engine noises on initial startup are not " issues " with these engines but a continuing noise is a problem.

BoeTieBandit - Thank you for the info. I'll take it back to the folks that tell me 'they all do that'. I'll let you know what happens.

bowtiebandit - next time I'll get your name right. Sorry about that.

BowtieBandit - I finally got my Yukon back to the dealership and got the same answer to my complaint - they all do that. I presented them with the printout from this forum and they had to confer with GM on what to do. They had me bring the car in and did the 'de-carbon' routine and replaced one spark plug. That, to the surprise of the dealer, made the noise go away.
I forgot to mention that this particular Yukon is a bi-fuel vehicle. I have a propane conversion on it and run on propane about 90% of the time. I am surprised that there is a carbon buildup running on propane.

Wow! If the de-carbon treatment actually works, then this thread should be "stickied" in any GM forum where this engine appears (hint, hint: Suburban forum) for all to see:D

I have a 2002 Yukon with 25K miles on it and it has been making this noise. I have had it checked by the dealer and they gave me a printout of the statement that was noted earlier in this chat thread. However, the noise has not been going away after the engine warms up. GM states that the noise usually goes away a couple of minutes after startup, but I have found that that is not the case. It is a really bad sounding noise for a gas engine to make and even noticeable by individuals with little or no automotive mechanical aptitude who even make a statement that "something sounds wrong".
I am planning on taking the Yukon back in to another dealer for a second opinion.

Originally posted by imatexan
I am planning on taking the Yukon back in to another dealer for a second opinion.
Let me know how it goes... the dealers out here blatantly denied the existance of the knock.

I too have a Yukon with the "clicking" sound. It has 33,000 miles and has had the full time clicking sound since I bought it @ 20,000 miles. Now it has an additional clicking sound only on cold start that goes away in less than a minute. The original sound remains. I brought it in to 2 different dealers at least four times over the past year to document the complaint. I also was given a copy of the document saying that this was normal. I have owned cars for 40 years. Most reached over 150,000 miles. Ones that made such a sound, and was not a diesel, had a problem.
Is there any info on engine failure as a result of this "normal sound"? Failed pistons, valves, etc.? I suspect that this is a real problem, but GMC's plan is to deny it, knowing that is cheaper to fight it out on an individual basis than to have a recall.

Regard General Motors Top End Cleaner to correct the problem of engine ticking on start up. I have a 2001 Chevrolet Lumina (car) 3100 V6 that had all of these symptoms and similar dealer stories. I tried the Top End Cleaner recommended by bowtiebandit, and although it didn't make the noise go away entirely it did minimize it to the point of not being outwardly noticeable. It now goes away in a few seconds, rather than in minutes. More over this is an amazingly quite engine once it's warm and believe it or not it's a bit quieter now at full temperature. I also switched from 5w30 oil to 10w30 which is OK per the owners manual. Not sure if this did much, but I believe an oil change after such a procedure is a must. What's interesting is that the dealer recommend some "sort of chemical engine cleaning" for over $100 dollars to solve my particular problem. GM's Top End Cleaner sells for $7 at my local dealer. Just find a vacuum port that allows the stuff to enter the manifold directly. On my engine the throttle body is lower than the intake plenum so it doesn't work well using their directions. Hope this helps some of you.

@ 60k miles mine still has the knocking. But if you say that the Carbon cleaner works i will try it and hopefully it will fix the problem. Thanks for the sugestion

The noise is called pinging. If you put Super Unleaded in the vehicle it will go away. They are teasted with fuel that is alot better quality than we get at the pumps, try another gas station too. On older vehicles you can correct the problem by slowing the timing down.

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

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.

:banghead: 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. :naughty:

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.

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.

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