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Knock Knock….It’s Your GM Engine Knocking

June 07, 2012 By: LemonLaw Category: cadillac, chevrolet, engine knock, GM, gmc

It’s a problem we have seen for over a decade– a piston slap and engine knock on cold start with various General Motors vehicles. Now, the latest technical service bulletin is out and it includes 2012 models as well.  Here’s a copy of the TSB courtesy of our friends at (website no longer available, links removed).

The most current models affected are 2007-2012 Cadillac Escalade, 2007-2012 Chevrolet Silverado, 2207-2012 GMC Sierra, 2007-2012, GMC Yukon Denali, and the 2007-2012 GMC Yukon XL Denali equipped with the 6.2 liter engine.

According to the TSB, the noise may begin in the first 12,000 to 15,000 miles and lasts between 5-30 seconds.  The noise is more noticeable when the weather is below 50 degrees.  The engine knock may be caused by an interaction between carbon that has formed on the piston, the piston motion, and the cylinder wall.  GM engineering feels that this engine knock or piston slap is not detrimental to the vehicle.  We are not so sure of that.

If you have been repeatedly for your General Motors engine knocking, it is essential that you look into your rights under State Lemon Laws and Federal Warranty Laws.   You could be looking at recourse and the help is free.  Contact a Lemon law Lawyer in your state for more information.

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28 Responses to “Knock Knock….It’s Your GM Engine Knocking”

  1. #1 LemonLaw says:

    @Brian: If you go to, we will be glad to review your claim free of charge to see if there is something we can do.

    • #2 Derrick Tillison says:

      I have a 2007 Escalade that’s paid for, the engine knocks real bad. What’s me recourse. Please help.

      • #3 Mike Bresnock says:

        72,000 miles engine noise until engine is warm….sounds like ticking then goes away. Particularly noisy in cold temps.

        I would like to have this fixed!

        • #4 Devon says:

          I have a 2007 GMC Denali with a bad engine knock what can i do.

          • #5 Brian Camp says:

            I have a 2007 Denali that knocks heavy at start up in any temperature. After the knock dissipates a ticking is noticable during slow and medium acceleration. The tick be ones more rapid as speed increases.

            • #6 Mark says:

              2011 GMC Sierra 6.2 engine, bought used with 50k miles, paid cash, engine knocks especially at cold temps, truck surges at stop signs and intersections.

              • #7 Mark says:

                I have a 2007 Denali with 102k miles and it doesn’t matter what the temperature is outside my truck knocks for the 1st 15 to 20 min before going away……

                • #8 William andrews says:

                  My 07 escalade ( 6.2 L ) has a sever piston slap . Started about 58,000 mi. .After three trips to the Caddy dealer in Pgh. and many calls to G M C I have learned they are very aware of this but no call back . I now have 90,000 mi. The slap has turned in to a violent knok @ all temp. .I have owned GMC all my life , always got 265,000 to 325,000 mi. before selling or trading in . I am a professional engine builder . Now @ 70yr. old. I no longer can do my own repairs .I finially got my wife & I abeautiful

                  • #9 Vic says:

                    I own a 2007 Cadillac Escalade EXT. I am having the same cold start piston slap that does not go away in tell the engine reaches normal operating temperature. Even at normal operating temperature I can hear a slight knock. Now the fact that GM discontinued the L92 gm goodwrench crate engine and replaced it with a new L92 crate engine part number 19329865.
                    GM says its a new improved version of the L92 has better hyper alloys that don’t expand as much allowing tighter piston to wall clearances.
                    no more knocking is a good thing…GM should make the knocking issue a recall, it’s embarrassing driving around in a fancy Cadillac Escalade EXT….. the flagship of pickup trucks with a knocking noice, a knocking noice that brings thoughts to mind like………wow that noice sounds so wrong on a $75,000 Cadillac, is my engine going to blow up.

                    • #10 mara says:

                      Just reached 71,000 miles on my 07 Cadillac Escalade EXT. I have lost sleep for the past two weeks with this engine knock tick or whatever you want to call it. I have been in and out of the shop and still going without any resolution. I’m hoping to receive some help from people that have same problem. Please help…Freaking out!

                      • #11 John says:

                        I have a 2010 Cadillac Escalade with 64,000+ miles on it. The engine knock started about a week ago and it do not matter what the temperature is outside. Even when the SUV warms to the proper temperature, the knocking is there. The oil pressure is fine so that is not the issue.
                        It is not good riding around in a $75,000 automobile and the knocking announce your coming.
                        What will be the next step to resolve this issue? Any help will be greatly appreciated

                        • #12 LemonLaw says:

                          @John: I would reach out to GM to see if there are any silent warranties for your year, make, and model.

                          • #13 Carolyn says:

                            I have a 2011 GMC Denali paid Cash is nocking bad took it too GMC will not do anything with me to pay my engine but I paid cash for this the same in GMC should take responsibility I’ve read the reports and I’m disgusted i have a 1995 GMC truck have over three hundred and thirty thousand miles on it with no problem

                            • #14 LemonLaw says:

                              @Carolyn: Now I see what you are speaking of. Please contact NHTSA at to see if there are any recalls or technical service bulletins.

                              • #15 Owais says:

                                Hi, I have a 2008 Gmc yukon denali with 6.2 v8 engine 108500 miles, it knocks at cold starts up for 5 seconds and the noise goes away as the engine temperature comes to normal. What is the next step to solve this problem?

                                • #16 Paul kelly says:

                                  I have a 2013 Silverado with 31,000 mi.
                                  Sounds like a thrashing machine for about 5
                                  Minutes. After start. The dealer agrees something
                                  Is wrong but Gm won’t do anything.

                                  • #17 Brandon MacKinnin says:

                                    ’07 Yukon Denali. Came from California. Engine knocks when cold for 5-10 minutes. Has 155,000 miles on it.

                                    • State: Alberta Canada
                                  • #18 Benjamin J Liell says:

                                    2008 Yukon Denali with 6.2 and piston slap. Not the original owner, just bought it.
                                    Any recourse?

                                    • State: MI
                                  • #19 Rob Mcgonigle says:

                                    I have a 2010 silverado that sounds like a diesel it has 35000 miles I just paid 20000 for and I think I’m going to let them take it back I’ll just continue driving my 04 silverado

                                    • State: Pennsylvania
                                  • #20 Shawn says:

                                    2012 GMC Sierra 1500, 11,000 miles started hearing ticking/knocking on start up, it lasted about 15-30 sec. the local dealer said it was normal, for louder and longer around 25-30k miles, brought to the same dealer, they said the same thing, I’m hit 60,000 mile, brought it back to the dealer, they told me it was carbon buildup, they did a carbon clean and told me to drive it for a 1,000 miles. I drove it as they said, still making the noise, I brought it back to the dealer now that it’s out of warranty they told me the engine needs to be replaced for $7,000 plus dollars. Real nice GMC

                                    • State: Ct
                                  • #21 T.B says:

                                    I have a 2012 Serria Denali 6.2l the engine is knocking took it into a shop they said it was the timing chain when I took it to another shop to double check they told me it’s a commen issue with these engines. GM knows about the engines being shitty and won’t do anything about. No recalls on them either.

                                    • State: Saskatchewan, Canada
                                  • #22 Frightened says:

                                    2012 Denali here, same problem <60k miles. I'm very concerned.

                                    • State: NY
                                  • #23 James says:

                                    2013 Sierra Denali 1500 6.2L 57000 knocks at any temp until the engine warms up. It is worse when the temp is below 50 degrees. The dash is also cracked. This GMC has been nothing but a disappointment!

                                    • State: SC
                                  • #24 Jerome Sterling Hicks says:

                                    2008 yukon xl slt 5.3L with a tapping lifter, right after 2k in transmission , 800 on bad electrical wires, 1200 on both axles , cv seal rotors and brakes, and now the tapping, and of course its paid for…thx GMC for your long lasting junk! Ford, Toyota, Honda will get my money from here on, i have been a GMC owner since 1987, really disappointed in America’s foremost auto manufacturer.

                                    • State: Maryland
                                  • #25 Juan ibarra says:

                                    I have a 2007 Escalade , it has a nosie knock at cold start , it will knock for about 2min then it will go away , I just ran out of factory warranty what can I do

                                    • State: Texas
                                  • #26 Tom Royal says:

                                    2007, Piston Slap like everyone else, very embarrassing. I don’t even like to move the truck in the mornings.

                                    • State: MD
                                  • #27 blake says:

                                    Same here, any help makes it hard to sell……

                                    • State: mi
                                  • #28 Chris Kelliher says:

                                    I own a 2008 Denali 6.2, we purchased the vehicle with 35,000 miles we now have 138,000 miles. The engine has always ticked until it warmed up every day, every start cold in morning in a heated garage in winter or cold start in summer. Mention to dealership and was told its normal and that if it goes away when warm not to worry about it so we live with it to this day. Have been looking at rebuilding the engine and keeping vehicle because its in great condition. every time I start it I’m reminded of the noise.

                                    • State: South Dakota

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