Important! Knock on warm start!

[dogfish246]

OK, I drove home with my car running great and when I got home I pulled into the driveway and shut the car. Then one min later, I got in my car and started it up, it knocked (sounded metal to metal). I shut the car and started it again and it knocked again from the engine. Only on startup and it only knocks once.

Any ideas, just got the car with 67k LT1? It was super well taken care of, look at my link below to see my Vette if you like.

Basically on startup it knocks once and kinda loud!

Thanks!

 

[jmccloud]

Knock upon start

Your photos show that you have an automatic.
My sister-in-law had a Chevy II (Nova) that did that (loud clank, metal-metal sound).
Found a cracked splice plate (holds the crank to the torque converter). If you can get your Corvette on a lift, it's easy to examine.
Good luck and congrats on a really nice ride.

 

[gmjunkie]

Your photos show that you have an automatic.
My sister-in-law had a Chevy II (Nova) that did that (loud clank, metal-metal sound).
Found a cracked splice plate (holds the crank to the torque converter). If you can get your Corvette on a lift, it's easy to examine.
Good luck and congrats on a really nice ride.

Flex plate cracked or torque converter nut loose,it only takes 1 loose nut to make a heck of a noise!!

 

[dogfish246]

Any other ideas because the sound seems to come from the engine (near the top)?

 

[G Winter]

I have seen broken flexplates where you would swear you have a broken piston.

Glenn

 

[dogfish246]

Yeah, I dont want a blown piston. That would be BAD!!!!!

Any other ideas?

 

[G Winter]

Try varied loads , see if you hear anything. Broken flex plate will usually start making noise under other conditions.
Only other thing I can think of is if you have a head gasket leaking water into a cyl. That actually could break a piston.
Maybe pull the plugs cold and see what they look like.

Glenn

On second thought. If it knocks after only a min of sitting then you would not be able to crank it over after a few hr if a head gasket was leaking. The cyl would have enough water in it that the piston would hit it.

 

[dogfish246]

Im pretty sure the car runs smooth with no noise at all loads. There is about 6in of snow and unfortunately my car wont see the road for at least a week. When I heard the noise it is only on startup. I never heard the noise otherwise, even at hard acceleration.

Any ideas?

 

[dogfish246]

It only has happened (so far) on a warm start. I drove the car for about 45 min and then shut it and started it. If I let it sit for a little in this cold weather, it starts normally. Cold starts are normal too.

I dont get it?