What is the Piston Slap issue all about?

[Bandit67]

We are picking up our new 2003 Denali XL today, and I have heard talk of some of the GM motors having what is referred to as 'piston slap'. I believe I've seen people talk about some of the Vortec 6000 V8's having this problem, so I'd like to get an idea of what it is, so I'll know what to keep an ear out for. Since I drive a diesel V8, I may unintentionally overlook noises coming from a V8 gasser, since every gasoline engine now sounds to me like it isn't running (I find myself checking the tach all the time).

[camdadz28]

Bandit67
I have a 2001 Yukon and 2001 Yukon XL and they both developed the piston slap noise you are talking about around 14 to 15,000 miles. The dealer says that this is normal and not a problem. The noise is most noticeable when you first start up the engine cold. It is a tap tap noise from inside the engine. Almost sounds like bad lifters. The noise subsides quickly and only returns after you have let the enigne completelty cool and restart. The dealer said that the reason for the noise is carbon build up in the trottle body. Sounded strange to me when it was explained. The dealer cleaned out the trottle body on the XL with a special spray and also sprayed this into each spark plug slot. This has to sit over night. Then they run the vehicle up to temp and this is the clean out procedure. It did work for about 10,000 miles. The Yukon has not had this procedure done yet and it tap, tap, taps every time I turn it on. It does go away before I can even get out of the garage........... and according to GM, It is not a problem. Hope this helps and enjoy the truck. I love both of mine.
I just got a new 2500 HD with the 6.0 V8 and I am sure it will get the same piston slap.

[GMMerlin]

I own a 02 Sierra truck with 47000 on it now..no problems with the cold start knock....
I usually don't get involved with "hot bed" issues, but I will give you this bit of information straight from GM. (only reason is because at the bottom it says to share the info with customers).

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.

[Bandit67]

Sounds like a cleaner such as 44k every 10k miles should keep carbon build-up under control. Although I have to wonder how buildup is occuring with all the detergent gasolines on the market these days.

[denaliman]

Hello gang, I'm a 23 year service Director at a G/M dealer. Here is my take. G/m is not happy with thier little problem. They have thier heads buried in the sand hoping it will go away. But try as they might the beat (knock) goes on. I also have 02 Denali with a 6.0 that has 15k and the cold morning knock just started in mine. Yes, doing a top eng clean works as a temp solution. The squid technique works the best. This drops the top engine cleaner into each spark plug hole and then cycles the pistons up and down with the chemical in the bores. After this method you clean out the engine oil with an engine flush. Here is what G/M will not tell you. I have replaced now 6 engines in the last 5 months that have blown up with low mileage, less than 20k miles. Two as low as 5k. All were maintained (oil changed) normally. All let loose with broken piston skirts. Knock, knock who's home, get it. Short piston skirts, out of round holes and carbon build up. Pistons rocking and the engines knocking. Ouch ,we have a problen Houston! All complained of cold morning knock. Yes, all were taken apart by my techs and we found that the cyld walls were crosshatched nicely, but the cyld walls were out of round by as much as .50 thousands of an inch. Now having done about 20 engines for excessive oil consumption and cold morning knock I can tell you that all the engines have out of round cyld walls. It is my opinon based on my evidence that G/M has several problems that they do not want to take care of. Even though I work for the General, my District Service Manager would not auth a replacement engine in my own vehicle. Let's just say that I'm more than unhappy. Just wanted to let other people know that the Denali is a great machine, G/M is going to have pull thier head out of the sand and take care of us. Thier future sales are hinged on thier current customers. I do know that they coated the pistons mid year in 03. Your dealer can run the vin on your machine and let you know if your's in an effected engine. The 03's so far do not have this problem at lower mileage. So time will tell as the coating wears if the noise will be previlant on the newer engines. Got to love em. Peace.

[Supra_Denali]

Originally Posted by denaliman

Hello gang, I'm a 23 year service Director at a G/M dealer. Here is my take. G/m is not happy with thier little problem. They have thier heads buried in the sand hoping it will go away. But try as they might the beat (knock) goes on. I also have 02 Denali with a 6.0 that has 15k and the cold morning knock just started in mine. Yes, doing a top eng clean works as a temp solution. The squid technique works the best. This drops the top engine cleaner into each spark plug hole and then cycles the pistons up and down with the chemical in the bores. After this method you clean out the engine oil with an engine flush. Here is what G/M will not tell you. I have replaced now 6 engines in the last 5 months that have blown up with low mileage, less than 20k miles. Two as low as 5k. All were maintained (oil changed) normally. All let loose with broken piston skirts. Knock, knock who's home, get it. Short piston skirts, out of round holes and carbon build up. Pistons rocking and the engines knocking. Ouch ,we have a problen Houston! All complained of cold morning knock. Yes, all were taken apart by my techs and we found that the cyld walls were crosshatched nicely, but the cyld walls were out of round by as much as .50 thousands of an inch. Now having done about 20 engines for excessive oil consumption and cold morning knock I can tell you that all the engines have out of round cyld walls. It is my opinon based on my evidence that G/M has several problems that they do not want to take care of. Even though I work for the General, my District Service Manager would not auth a replacement engine in my own vehicle. Let's just say that I'm more than unhappy. Just wanted to let other people know that the Denali is a great machine, G/M is going to have pull thier head out of the sand and take care of us. Thier future sales are hinged on thier current customers. I do know that they coated the pistons mid year in 03. Your dealer can run the vin on your machine and let you know if your's in an effected engine. The 03's so far do not have this problem at lower mileage. So time will tell as the coating wears if the noise will be previlant on the newer engines. Got to love em. Peace.

GM loves hding behind problems.. I am expecting my Denali Truck to arrive at the dealer in 2-3 weeks.. its a brand new 2004 Sierra Denali truck, will I have this problem? Makes me not want to buy this truck now.. I was originaly going to get the Cadillac Escalade EXT which has the 6.0 but has different pistons / heads or something like that which bumps the horses up to 345, does this motor have any problems with the tapping issue or is it just the 325 horse 6.0 in the Escalade 2wd & Denalis?

Thanks

[tonytone]

Originally Posted by denaliman

...I do know that they coated the pistons mid year in 03. Your dealer can run the vin on your machine and let you know if your's in an effected engine. The 03's so far do not have this problem at lower mileage. So time will tell as the coating wears if the noise will be previlant on the newer engines. Got to love em. Peace.

You may be right about coating the pistons mid-year '03, but I think that not all '03's (as you alluded to in your post above) so far are not exhibiting the problem--I have a model-year '03 YXL that clearly was built in '02 (I bought it in December 2002) and it is starting to exhibit the classic signs of piston slap that others have unfortunately experienced.

FWIW--I'm not slamming you in any way; in fact I am glad that there is someone out there in GM-land such as yourself, who is being straightforward instead of attempting to sugar-coat this issue.

[YukonDave]

I purchased a 01 Crewcab with the 6.0 new and started having issues at about 5,000. I'll tell you they got tired of see me come in to the dealership. When you purchase a 35,000 dollar vehicle you expect it not to have noises that sound like the engine is going to fly apart at any minute. The dealer told me to contact the 800# that was on the GM message and I did, they gave me an extended warrenty on the engine till 100,000 miles. This made me feel alittle better but I still hate that noise. It made me think twice before purchasing my next one but what can I say I'm a GM man. I purchased my 03 Yukon with a 5.3 and it know has 47,000 miles on it with no issues. Cleaning the carbon does help but only for a little while I don't think I when 2,000 miles and it came back. I am concerned about putting that cleaner in the cylinders and pistons, removing oil from the pistons and walls can't be a good thing. I still love my GM vehicles though.