Rich Farr

I started my 2010 with 25,000 miles on it this afternoon. Started instantly. Smoke came out of exhaust at point of ignition. Then hammering at idle. Immediately shut off engine and checked oil - was surprised how dirty when last change was only 3000 miles earlier. No oil used.
I restarted the engine and it continued to hammer on one cylinder. After 4 minutes completely quiet. I drove three times this afternoon - perfectly quiet.
Any comments would be greatly appreciated.

Rich

AORoads

No idea, but I'll take a wild guess: something bad going on with that one, hammering cylinder. You're braver than I am. If I heard that kind of noise, I'd shut it off like you did, and have it trailered somewhere for a look-see. Whatever it is, the damage's done now.

Let's see who comments further.

EVRose

Did you notice what your oil pressure was on start up? I dont know why but I got into the habbit long ago of watching the oil pressure gauge every time I hit the start button.

okie08vette

Sounds bad to me I would have it checked out.

philip_g

2010 with 25k miles? Sounds like a trip to the dealer to me.

R&L's C6

Good thing you have lots of warranty left...

42Chevy

Same here. Sounds like possibly a pressure issue. With out hearing it that is my best guess.

vet55

+ 1

michaelinmech

A failing hydraulic lifter ?

Rich Farr

The engine started at first touch of starter button. First thing I looked at was oil pressure before I shut it off. I had a similar experience with my 2005. Started 35f degree weather and heard sticking lifter sound. I did not notice any smoke. I had oil and filter changed immediately and never had problem in next 30,000 miles. At the time there was some comments about possible issue with oil filter.

In Canada warranty is only 36 months!

Years ago we had a GM van with a constant knock - GM said they all did this and refused to do anything under the power train warranty. I sold the van and found out two years later it was stilling running with the noise and still no issues.

I am sick of GM quality issues and picking up my replacement for my Cadillac CTS this week. I am supporting the American economy by buying a car with the highest U.S. content - a 2013 Toyota Avalon!

philip_g

well, maybe. IDK what the warranty is in canadia.


EDIT: answered above, bummer.

irok

powertrain warranty is 5 years in Canada not 36 months.

bolivar

Cadillac Northstar motors have something called 'carbon knock'. Northstars driven 'carefully' will carbon up. Sometimes a piece of carbon will come loose from the top of the cylinder and stay in the cylinder and stick up enough that it will hit the head when the cylinder comes up. This sounds terrible and gives a loud knock. Northstars can be 'blown out' with fast high rpm 'wide open throttle' runs to redline in the lower gears and get rid of carbon buildup. This carbon buildup also happens on the rings and causes excessive oil usage by Northstars. The WOT runs will do a lot to get rid of a carbon knock and will also free up stuck rings and reduce oil usage.

I really don't know if our Corvette motors have this problem. Frankly, I've not read anything like this on this forum. People are saying you have a 5 year (100,000 mile?) power train warranty. Read your manual in the warranty section. If you have the warranty, and you seldom or never drive aggressively, a few WOT runs might just cure the problem. If you break something, you are still under warranty (so someone else says).

Premium gas also leads to this problem, surprisingly. Premium 'resists detonation' and will form carbon more than a car using regular, and little old ladies and men driving their Northstar carefully have this problem.

If it is a lifter or main bearing problem, I think I would like to know about it now rather than later when it has no warranty. So, take it out and drive the P*** out of it. It will take accelerations, not high speed to 'blow the carbon out'.

bolivar

Another 'wild a** guess'. What color was the smoke? Blue is oil, white is gas (or coolant). If it was white, you might have had an injector stick open at the previous shutdown, a cylinder with a stuck injector was filled up with gasoline. Could it have been enough to have a hydrolic knock from a cylinder full of gas????? The sticking injector might also been leaking gas into this cylinder and also getting by the rings into the oil which caused the oil to look bad when you checked it.

I'm looking for help here for me and especially for you from our more skilled mechanics on the forum.

Might you also have a blown head gasket and you had a cylinder full of coolant at the startup? This leaking into an oil passage or past the rings would also make the oil look terrible. Northstars also have head gasket problems. If the gasket is blown from a cylinder to a coolant passage (the usual problem with Northstars) you will have massive overheating when the motor is pushed or driven up a steep hill (putting a high load on the motor).

Come on experts, check in on this guys problem. He's given a good description of what happened, some of our experts have seen this problem???

BettermostCorvette

My guess a clogged weeping injector. Did it throw a code?

Steve_R

First, oil used for several thousand miles SHOULD look "dirty," that means it's doing its job.

Second, if a cylinder was full of fuel or coolant (or any other liquid) at startup the motor would hydrolock. You'd know immediately if that's the case as you'd probably have a hole in the block and the motor would be destroyed.

Hard to diagnose the OP's problem; not enough info given. As said previously smoke color gives an indication of what was in the cylinder(s).

AORoads

so then it's down to smoke color: black or white (think it's unlikely) or the old "blue" or gray for oil. which one?

richietables

I suppose it's all well and good to try to do a long distance diagnosis but I would take it in and find out for sure what's up. Sooner the better. Good luck and keep us posted.

My 2 cents...

Seadawg

And, if it were me, I'd do this CAREFULLY, again CAREFULLY - I would start the car cold, get behind it, and sniff the smoke for exhaust odor. Not with my nose stuck up the tail pipe, but close enough you can feel the flow of the exhaust.

If the car is cold, you should get some odor, but once it warms up, you should not be able to smell anything.

AGAIN, don't stay there and do this for more than a sniff, because you WILL get carbon monoxide into your lungs, but this is a quick/easy check on any modern car for engine health. Meaning, if all of the systems are doing their job, very little pollutants should be coming out of the exhaust, only carbon dioxide and water vapor.

weathermaker

Was it a "hammering" or a lifter "ticking". Lifters can sound serious if you never heard it before.