Hi All,

I recently purchased a 2018 C7 Z06. This is my first LT4 vehicle. I have had LS6 & LS7 Corvettes prior. It has very low miles (only 200!). The poor thing needs to be driven. I noticed an engine noise shortly after taking delivery. I have an automotive background - the first thing I did was exchange all the fluids. The engine oil looked fairly clean but it was a no-brainer since I didn't know how old it was or what type of engine oil was used prior. I used an OEM filter and Mobil 1 Advanced Synthetic (Dexos1) 5-30WT to be run for the remainder of the engine break-in period (1500 miles per the owners manual - I may change the oil again sooner than that to take a closer look at the oil). The engine now has 500 miles (I added 300) and the noise is the same - see the attached video.

The noise *seems* to be coming from the lower part of the engine (although it could be misleading or even be coming from the bellhousing area, etc). I did take the time to put my ear to a long, thick screwdriver while the car was still on my QuickJack to check various areas. I checked the top of the engine (put did not pull the plastic valve covers - yet), the alternator, supercharger fully area & other parts of the front of the engine and on the oil pan. No obvious amplification of the noise at my ear when using the very large screwdriver as a stethascope. No change in the noise if I push in the clutch (manual trans car). Soon I will listen to the A/C compressor and also get the car back in the air to listen near the bellhousing and anywhere else I can think of.

> The noise is only at idle and slightly above. The noise goes away if I raise the RPM's above 1500 or so. The noise totally goes away after the car is fully warmed up and driven away. It does not return until the engine has cooled back down. <

Being that the engine has such low miles I would suspect a possible cranky lifter although I have seen little to no complaints over the years regarding low mileage LT4 cars having lifter issues from sitting. Plus the sound does not have a rhythmic tap-tap-tap that changes with engine speed. It's more of a mechanical rattle. Hard to imagine it would be from any other part of the driveline though with such low miles. I am about ready to try an oil additive just to be proactive but those are really meant to help remove any sludge on a higher mileage engine if it has a noisy lifter. I'm stumped so far.

Please listen to the video and chime in if you have any suggestions or have heard this noise before.

 

Could be that pesky belt tensioner. But with only 200 miles hard to believe it would be bad. They are filled with oil so it could leak out if seals got dried out. See any sign of this? Or leaking anywhere for that matter?

 

Get a mechanics stethoscope, touch the tip on various parts, it might be more sensitive than a screwdriver.

 

dump the oil and filter. replace. drive the car for a few days and see if everything loosens up and if the noise continues. if it does need to pull the v/c and dig deeper. with only 200 miles win a 8 yr old car a stuck lifter is very possible.
once you drain the oil after a getting it up to temp take a sample to send to Blackstone. this will help determine where the noise is coming from

 

Have you tried going to 4 cylinder mode to see if the noise changes?

 

If you have changed the oil, drive the car for a while. I have driven an LT4 engine over 72K miles and it is just a noisy engine. Since this car has no miles on it, drive for about a 1K mile and see if noise goes away. I have listened to the video and I do not really hear anything unusual, but possible the belt tensioner could be noisy from sitting & lack of use. Drive her for a few miles & go from there.

 

Sounds like my LT1 with 30,000 kms on it, so normal?

 

Get a mechanics stethoscope, touch the tip on various parts, it might be more sensitive than a screwdriver.

Thanks - that is next on my list. But I will say my ear pressed on an XL Snap-On flat-blade really picks up the nuances well. I can here all kind of other subtle normal mechanical sounds while searching.

 

If you have changed the oil, drive the car for a while. I have driven an LT4 engine over 72K miles and it is just a noisy engine. Since this car has no miles on it, drive for about a 1K mile and see if noise goes away. I have listened to the video and I do not really hear anything unusual, but possible the belt tensioner could be noisy from sitting & lack of use. Drive her for a few miles & go from there.

Thanks - I will drive longer and also take a better video once I am under the car swapping out the oil around the 1000 mile mark. I may use the Mobil 1 Advanced Synthetic again at that time. I have Mobil 1 Supercar patiently waiting. The sound bounces nicely off of my garage floor but I will take a better mic'ed video when I get the car in the air again. It bothers me that it does disappear once warm (and I am a bit lifter sensitive coming from the LS7 world - lol). I suppose that could be a blessing in disguise as it could be something worse. Definitely going to check the tensioner closely very soon.

 

Sounds like my LT1 with 30,000 kms on it, so normal?

It is possible. My first LT4 and now I need to listen to other LT4's in my Corvette club. Wish there was a Corvette-specific shop in my immediate area with an LT4 specialist on board. Someone who hears these engines on a regular basis.

 

xxx

 

I have not. Don't think it will go into 4 Cyl mode stopped and idling. But I could try that on the road and see if that makes any changes when cold. Thanks for the input.

 

Thank you - I went over the powertrain and chassis with a flashlight quite carefully when I first got the car in the air (and before noticing the engine noise). But now I will focus on the vicinity around the tensioner as well as take a stethoscope to that area.

 

Thanks - this may be the direction I take after driving another 100-200 miles and no other resolution.

 

Hello,

My car has about 52,000 km and makes the exact same sound, genuinely identical. I have posted a few times in the Facebook groups, and everyone said it sounds normal. I am also pretty particular about noises that feel out of the norm, so I completely understand the concern. Mine is an M7 car as well. I have driven it extremely hard for the past 30,000 km with no issues, and the engine has always sounded the same. When I switched to fresh Red Line 5W 40, it did quiet down significantly when the oil was fresh.

Next month I am planning to swap to Mobil 1 Supercar 5W 50 and add Ceratec, and I can report back with what I find.

 

It will do 4 cyl mode while idling in eco mode.

 

Thank you! I will still take a video directly under the car to single out the noise when I R&R the engine oil again. Your comment is reassuring to hear but having the engine noise go away once fully warmed up and driven rubs me the wrong way. Yes, please let me know how it goes on your end. I have Supercar 0-40wt waiting in the garage.