2011 GMC Sierra loud knock on startup

scott.hartman.589 · November 4, 2014

Ok so I bought my truck used with 81000 on it 6 months ago, the day I bought I took it back with a chirp sound. Turns out the cam shaft was bad dealer fixed no issue with that. The truck was quiet and ran well. So I have put 5000 miles on it and now it sounds like a diesel when it first starts up. It lasts about a minute the it's not there. I have read piston slap and that it is nothing. To worry about but it really sounds bad. I took it back to the dealer and they said they didn't hear anything that wasn't normal. But I have friends with the same truck and theirs don't sound like mine. I still have the power train warranty and am wondering if anyone has had success in getting this fixed. I think it's crap that this is considered normal. This could be the last gm product I buy

gmtech4 · November 4, 2014

Different dealer or call regional service manager ,

Also drive with the shop Forman or service manager , getting a little mad never hurts

'01LS1 · November 4, 2014

Check your plug wires. My 2013 was bought new & had a progressive strange sound at start up. I say strange as it was not the lifter tick nor a metal on metal slap. Got to looking around & one plug wire, while on, was not completely clicked on. Strange sound went away. May not be the issue, but takes less than 5 minutes to check both ends of each wire.

& this will NOT be the last GM vehicle I buy. <~ ...couldn't resist.

00Silverado4x4 · November 4, 2014

Do you have any exhaust manifold bolts broken off? These engine have a knack for breaking off those bolts. If you have a broken bolt or two you may have a minor exhaust leak until the engine heats up and seals itself.

MaverickZ71 · November 4, 2014

The prior generations were known for piston slap (my Dad's old 2002 Silverado used to knock like a loud diesel), but the GMT-900's are more known for lifter tapping, especially with the AFM lifters. They will sometimes clatter until they get pumped up full of oil, or they can completely go bad and then you have to have your engine rebuilt with new lifters and possibly another new cam.

GMCustomerService · November 4, 2014

Ok so I bought my truck used with 81000 on it 6 months ago, the day I bought I took it back with a chirp sound. Turns out the cam shaft was bad dealer fixed no issue with that. The truck was quiet and ran well. So I have put 5000 miles on it and now it sounds like a diesel when it first starts up. It lasts about a minute the it's not there. I have read piston slap and that it is nothing. To worry about but it really sounds bad. I took it back to the dealer and they said they didn't hear anything that wasn't normal. But I have friends with the same truck and theirs don't sound like mine. I still have the power train warranty and am wondering if anyone has had success in getting this fixed. I think it's crap that this is considered normal. This could be the last gm product I buy

Hi Scott,

I'm sorry you have concerns with your vehicle. I understand that you are unsatisfied with your dealerships diagnosis. If you're interested in a second opinion we'd be glad to locate another dealership your area and schedule an appointment on your behalf. If any additional assistance is needed, please let me know!

Andraya

GM Customer Care