2003 Gmc Yukon - Bad Knock

177mph · January 4, 2011

My 03 Yukon (5.3 V8 - 94k miles) usually has a little knock at start up - but now with the cold weather its gotten much worse. Its now lasting a good 15-25 seconds after start up. Sounds like a rod knock - then goes away. Truck runs great - no codes - doesnt use any oil. I was always told this was a piston slap issue and that it could not be avoided. Does anyone have any more info than that?

8.1HD/ALLISON · January 4, 2011

Sounds about right. Only think I know to try is to remove spark plugs and carbon soak the top end with some top end engine cleaner. It might help some, but probably won't completely go away.

rdnkcpa · January 4, 2011

Is it a rod knock, or a stuck lifter? How is your coolant level? If you have coolant loss and no leaks you have problems. My 2004 did the same, stuck lifter was the problem among others.

177mph · January 5, 2011

Is it a rod knock, or a stuck lifter? How is your coolant level? If you have coolant loss and no leaks you have problems. My 2004 did the same, stuck lifter was the problem among others.

no coolant loss, no leaks. besides the first 25 seconds - the truck runs great!!