When I dropped off my car for some warrantee work, I told the service advisor my engine had an unusual noise at 2300 - 2800 rpm under light load. Difficult to describe, not valve train, piston slap, etc.

They had no trouble reproducing the noise in the shop. They described it as a rubbing noise, internal to the engine and near the rear.

I have an ongoing oil consumption issue since NCM delivery (1500 miles/qt with very conservative 20,000 miles on my 05). They will not address the engine noise issue until GM gives them some direction on the oil consumption. I have done the GM oil consumption test which verified my consumption. Compression and Leakage are normal. Last week they scanned my car for hints on my driving habits, which the service advisor said was normal.

Service advisor is on vacation so I will not get anymore info until after the holidays.

What are the chances that these two problems are related? Do defective oil rings make noise?

 

Scanned your car for driving habits? Wow, that's scary! I had tyhe same issue and the guy asked me where I shift then proceeded to tell me I drove the car too hard. I told him its a friggin Corvette for god's sakes then pulled the motor and built one myself. There is a ton of stuff that can be the culprit, you'll just have to wait and see.

 

Scott, I have tried to answer your PM, but unfortunately it seems your over the size limit so it would not let me send the reply to you. To answer your question:

I cannot say that it has. Subsequent tests show that there is no leakage, but my usage hasn't changed much. There was one period where I went much longer for some reason, but I think it may have reverted back to normal form. I have long since resigned myself to adding oil as otherwise there does not appear to be an engine problem. I just don't have the time or patience to deal with the dealership anymore over this.

Good luck to you.

 

I had same issue with engine noise.. tapping and a thunking at about 1400 RPM.. brought car back to dealer and heres what they found.. The silver nitride on my lifters was missing so the lobes on the cam are worn away.. God knows where the metal has disapeared to but I am now awaiting an evaluation from GM to determine if they will replace my engine.. anyone with ticking or tapping better get the vehicle to a dealer and get it checked out.. The tech working on my car has determined that this was not anything I could have caused but is a factory defect.. by the way.. I have 35000 miles on this car and the noise started at 34500... If GM decides on no replacement engine I will be returning my Vette and purchasing a New Mustang !!!! I have owned Corvettes since 1972...

 

Not to ask a dumb question, but the ticking and tapping sound is louder than normal - correct? I ask because almost every new car I have ever had sounds a little like ticking and it is just the injectors firing quickly.

 

With the lobes worn away, did you notice a lack of power? GM mentioned they wanted the dealer to check my valvetrain but still waiting for a definitive course of action. I had an oil analysis done last year and it was normal. Did you have your oil checked at a place like blackstone labs?

 

After 4 days in the shop, they decided it was not the engine but the front bearing on the torque tube. They replaced the bearing but the noise is still there

 

 

Is the noise the same in nuetral with the clutch in or out. In gear with the clutch in... See if clutch position or in nuetral with the clutch out has anything to do with it. A change in sound with change in clutch position could indicate it's in the clutch/pressure plate area.

I haven't seen or run across a rubbing noise in the rear of the engine. Seen some strange clutch/pressure plate issues that can make noises.

A qt in 1500 may or may not be normal. All depends of driving conditions, oil age ... Old oil run hard after a lot of short drives will burn off fast. Example, drive for many months with short trips. That oil will accumulate a lot of condensation/combustion byproducts. Then take freeway blast on that old oil and it will appear to burn off fast.
That same car driven by a different person may not appear to burn off a drop. When I was at a dealer I saw that all the time, cars would get traded in by people that complained for years about oil consumptions, then the next owner has no problem at all.

The key to telling if nothing is wrong is the compression/leakdown tests and spark plug inspection. If all of those show normal, nothing is wrong. Combine driving habits with low mileage/short trip usage with manual transmission - maybe a lot of downshifting or some high RPM use ... and some cars will use a little oil.

The other thing to do is drive behind the car. Fully warmed up, have the person behind you watch for any hint of blue smoke. Normal driving, then do some full throttle accelerating, some coasting down. Not a hint of blue smoke in any of those conditions and it passes compression/leak down tests - nothing is wrong with it.