My GT does this too briefly when I start it in the morning.

That said, my 99 TA LS1 did it, and my 97 TA LT1 did it. I never had an issue because of it.

 

I used to get the slap back in Michigan on cold winter days. I moved to SoCal and even after work, when the car has been sitting in the sun and 70 degrees all day, I still get some very noticeable slap until I get to full operating temps. Mine has become noticeably worse. I have to get my front end repainted b/c someone backed into me, so while it's there, I'm going to have them look at it.

 

Rasing this from the dead:

I have a 2009 GT with 55k kms (34k miles) and have been suffering through the 5 minutes of slap on our frosty mornings. At temps well below freezing it makes lots of noise.

The dealer has looked at it and acknowledged the noise. They said GM Canada has never heard of a G8 complaint...The first step they are going to try is a decarbonization treatment. I can't see how this is going to help. Is this going to hurt?

Next step they wanted to possibly looke at the main bearings? Again I can't see why, if this is a spun bearing wouldn't the noise get worse with increasing engine temp?

Anyhow I am thinking of doing nothing if the noise is harmless. Is this harmless? This is going to be my last GM...

 

BS on GM Canada never hearing of this issue. I don't see how decarbonization would help since this issue is caused by piston to cylinder bore tolerance. What they need to do (unless it really is a bearing issue) is they need to take off the top end end measure the pistons and the cylinder bores to make sure the clearance between them is within the specified range of tolerance.

 

I agree. Will the decarbonization do more harm than good? Do I want a local shop disassembling my engine or just let the noise be?

 

If the slapping/knocking goes away once the car warms up to normal operating temperature, it's purely cosmetic. If it doesn't go away, you have a problem.

I noticed that using synthetic oil actually makes the cold piston slap worse. Try regular dino oil if you aren't already using it and see if it helps it a little. Again. Purely cosmetic though if it goes away in warmer (above 50 deg lows) temps and when the engine warms up. And piston slap isn't all that uncommon. My 2001 mustang gt did it; ford probe gt did it; the nissan 4-cyl altima I rented 2 days ago did it.

 

GM Canada is full of it, I can give you a file # and a name of whom I talked to about my car. Mines done this since new, its worse the colder the temp is and only knocks when accelerating. It will last 10-15 minutes until the engine and oil are up to full operating temp. I've given up on any action from GM.

 

I live in central PA my G8 GT Ticked for a short time when cold and would go away. I had it to the dealer who replaced the lifters. Tap still there but picked up the piston knocking noise. 40,000 miles.
I know my chevy 355 with forged pistons would knock when cold and then go away.
I have run synthetic oil since I picked the car up. I am concerned about the noises. I don't plan on getting rid of my ride. We will have to see what the dealer will do this time.

 

I had piston slap at 20k miles and got the engine replaced. I'm at 30k now and its back. I had it into the dealer and they said cyl. #5 was giving me the noise. It goes back in on Monday. This may mean engine #3. The invoice says the engine lists for 7k.

 

Hey RC

Sorry to here of your problems. Kind of make me glad I park mine in the cold months. Daily driver is a 02 Bonnie SSEI. Its leaking at the intake gaskets right now. Guess it always something with cars?

 

Until I get to the 5 year, 100k on the drivetrain I'll just keep on getting engines from GM until I get a good one

 

My G8 literally sounds like a diesel on cold mornings. Like stated above, its ok until I pull out of the driveway and accelerate and lasts 10 mins. or so until warmed up. I just bought my car last month with 16K miles on her, so I am really hoping it doesn't sound like this when it gets warmer.

Coming from a LT1 F-body, my old car never did this but I am well aware of the LS1 piston slap issues in F-Bodies, and I would have thought the newer generation V8 would have been a lesser problem by now.