2010 M45X Engine Knock

[njjuliano]

I started hearing engine knock on my car, 27k, a bit early on the oil change interval. It sounded similar to a knock that I heard before in the car's early life, and it was usually nearing the oil change interval, and seemed to be caused by low oil. I usually added a quart, noise disappears, go a few more miles, and get the oil change. This did not work this time. I added the oil and after a few days of driving still there. I went for the oil change, still no change. Drove around for a couple of days, and finally scheduled an appt.

Dealer had the car from Tues to Fri. Changed fuel damper, and after a few more diagnostic tests, could not isolate the noise to get a fix. Sent me back the car, and was advised to return when its louder and easier to diagnose.

Knock is definitely more audible. It usually just sounded on gear when idle, now it starts even on neutral. Car usually knocks under 500 rmps, now it knocks above.

Same as this guy, isn’t he on here? I seem to remember the avatar:
http://www.iscenem.com/forum/threads/24 ... le-in-gear


This is the knock
http://www.youtube.com/watch?v=A32KioBnvlc

http://www.youtube.com/watch?v=wtLeuOK2-Yw

He didnt get any resolution yet. I am ready to get the car back to the dealer, but wanted to get some help from the forum. Ideas? Any route to take? Advise to have them check?

Thanks.

[DeanM45]

Have them check the front dampner bolt (harmonic balancer). If OK then they should check thrust on the crankshaft.
It could be rod/main knock from your previous experience but I assume they checked oil pressure at the dealer and low RPM rod/main knock is USUALLY only present if there is low oil pressure at idle.

[njjuliano]

Very helpful. This is good to have. I dont recall them saying anything about doing an oil pressure check. All the effort done was isolating the noise so that they continue. They couldnt, hence waiting for a louder noise. Hate it to become worse, though.

[atlM35]

When driving, does the sound get faster as the RPMs climb?

[njjuliano]

A wee bit, and immediately disappears in higher appx 500 - 700 rpms. The rhythm definitely is slower in lower rpms.

[jonlex99]

That's plenty loud. I would go back to the dealer and have then diagnose some more. I wouldn't wait for it to get Lauder.

[lovemycarM35]

I had a knock in my 2007 M35 about a year ago and they had to replace the short block you have the 45 so may not be relatied

[njjuliano]

That's plenty loud. I would go back to the dealer and have then diagnose some more. I wouldn't wait for it to get Lauder.

Agreed. The info here would definitely help me once I get it back to them. They've been very helpful thus far.

[njjuliano]

I had a knock in my 2007 M35 about a year ago and they had to replace the short block you have the 45 so may not be relatied

I believe I read that, or was it an actual 45.... Either way, thanks for the info. Will add it to the possibles.

[trayday]

You could try and disconnect each coil one at a time and see if the noise disappears. If its under warranty I would just make sure the oil level is correct and beat on it until it gets worse.

[njjuliano]

I actually brought it back yesterday, as it was unseasonably warm, and the knock was more audible. Brought it in, and they said they didnt hear it. Apparently they said its magnified inside the cabin, but cant hear it outside. They used the stethoscope to isolate but cant seem to find it still. Im not sure what they cant hear, cause I clearly hear it standing right outside, with car on drive, when standing near the front driver tire.

Still looking for light at the end of the tunnel....

[njjuliano]

I have been keeping tabs on the vehicle's out of norm activity...here's a new one.

Car sat from Friday eve till Sunday afternoon. When I started it Sun, it had a quick hesitation, hard start, big puff of smoke out of exhaust. Then higher, louder knock on Park. Waited a few moments, and drove the car. Car returns to normal behavior, ie knocking on D/P when not moving.

Still "normal" today.

[njjuliano]

Has anyone else have any fix done for this knock? Other words to use so that the dealers are more willing to fix it, as opposed to dealer advising on waiting for it to get worse before they do anything.

[EdBwoy]

Sorry for having to deal with this for such a long time. Let's try to solve this before the drivetrain warranty runs out (or has it already?)
1. Have they put the stethoscope on the exhaust manifolds to isolate the precats?
2. It doesn't seem like your engine is shaking from the video, but is it shaking IRL? Also, does the sound change when you shift from P-R-N-D? Does it shake the car? If so, check the engine mounts. Those usually cause that deep knocking sound
3. How's your oil level? Have you had bad consumption problems since you saw the big puff?

[njjuliano]

Sorry for having to deal with this for such a long time. Let's try to solve this before the drivetrain warranty runs out (or has it already?)
1. Have they put the stethoscope on the exhaust manifolds to isolate the precats?
2. It doesn't seem like your engine is shaking from the video, but is it shaking IRL? Also, does the sound change when you shift from P-R-N-D? Does it shake the car? If so, check the engine mounts. Those usually cause that deep knocking sound
3. How's your oil level? Have you had bad consumption problems since you saw the big puff?

Warranty has not run out, I did purchase the Elite till 75k, 2017.

1. I was told at one of the multiple times I took it in, that they did, and that they didn't hear it, and cant decipher. It is very difficult to believe it since I can hear it audibly without any help standing outside the car, they have acknowledge the noise but deemed it normal.

2. Disclaimer, the video posted above is not mine, though it sounds very similar. I will take one for my vehicle though, and post it. The sound is not there on P, and rarely on N. It is there on D and R, consistently. When stopped on either D or R, I was idling at 400 - 500, really low. I addressed it multiple times, and they finally adjusted it to 750, and the noise disappeared for a bit. But it is back. I will inquire of the mounts in the next time I bring it in.

3. Oil level consumption is almost 1q per 1k. I usually add a q every half oil change interval, so after that big puff, it pretty much has stayed the same.

I was told that it was normal for the V8s, then after a while, somewhat relented and say its not that normal, but then again, its not that big a deal. I took it to another dealer, they acknowledged the noise, but was told that it needs to be louder before Infiniti can approve any fixes. Basically, they dont think its broken at this point.

It almost seems like either an easy fix, that can really be a big problem in the future. The worst part about it is the lack of clarity in the situation. Is it ok, or does it need to be fixed? Info in the interwebs is quite limited too. Getting a bit frustrating.

[EdBwoy]

We're getting somewhere.
1. So, on the precats, I'd say don't worry about it. It's not usually a "heavy", gear-dependent or continuous sound.

2. High quality video if you can, would be great.
The fact that the sound isn't there when in P, but is present in gear leads me to the drivetrain mounts again. Is either your engine or car shaking? Does the clunk get louder when shifting like from P-R or R-D?
Another way would be to just pop your hood and rev your engine. Don't ease into it, just blip the throttle suddenly and see if the knock persists.
You could also lift the engine slowly and see if the engine lifts up leaving the motor mounts attached to the frame. Warning, this could damage your mounts, so a better but more time consuming way would be to unbolt the mounts, lift the engine and see how loosely the mounts are attached to the engine.

3. Back to your hard start and the puff of smoke, did you hear any rattling or clunking sound while the car tried to start? Depending on what you find out about the mounts, this could become pertinent, but it's not really a big concern at the moment.

[njjuliano]

We're getting somewhere.
1. So, on the precats, I'd say don't worry about it. It's not usually a "heavy", gear-dependent or continuous sound.

2. High quality video if you can, would be great.
The fact that the sound isn't there when in P, but is present in gear leads me to the drivetrain mounts again. Is either your engine or car shaking? Does the clunk get louder when shifting like from P-R or R-D?
Another way would be to just pop your hood and rev your engine. Don't ease into it, just blip the throttle suddenly and see if the knock persists.
You could also lift the engine slowly and see if the engine lifts up leaving the motor mounts attached to the frame. Warning, this could damage your mounts, so a better but more time consuming way would be to unbolt the mounts, lift the engine and see how loosely the mounts are attached to the engine.

3. Back to your hard start and the puff of smoke, did you hear any rattling or clunking sound while the car tried to start? Depending on what you find out about the mounts, this could become pertinent, but it's not really a big concern at the moment.

1. Hear you.

2. No, the car is not shaking, neither is the engine, not visibly moving at all. will look again to make sure. And no, no clunk from shifting through the gears. I have revved it to see, and it certainly goes away after 1k. Both easing through and blipping through the throttle, same.

3. No rattling. It was that one time thing. Scared me crazy, and shut down car immediately. After that, had not had any incidents. One thing, however, my car certainly doesnt like short drives when cold, then not getting used till a few days later, like moving the car to another spot in the morning to get closer to the hotel. Staying in hotel for a couple of days. When I finally use the car, it will start, but with a bit of a tantrum.

[DeanM45]

After reading through this again with the updates I am leaning now towards one of two things:
1) Broken ring land(s) on one or more pistons
2) Missing C clip from one or more of the piston pins

When in P or N you typically have the most vacuum in the chamber (unless you are decelerating---can you hear the knock when decelerating ?(foot off gas from high speed))

[EdBwoy]

Sadly, I also suspect it's something to do with the pistons. [One time my M45 sat for about a month. Started her up, and it did throw one hell of a tantrum while starting, complete with a rattling sound...long story short, now It's sitting pretty in the garage with an engine waiting to go in].
The reason I asked about oil consumption initially is that broken rings will let a good amount of oil into the combustion chamber. Add that to the normal oil consumption of our cars (I mean normal in a VK45 kind of way) and it gets pretty noticeable. However, I know you are not experiencing low oil issues. I'd recommend you get codes pulled from your car even if the CEL is not on, just to see if the knock sensor detected anything funky. Also get the compression checked.

[njjuliano]

After reading through this again with the updates I am leaning now towards one of two things:
1) Broken ring land(s) on one or more pistons
2) Missing C clip from one or more of the piston pins

When in P or N you typically have the most vacuum in the chamber (unless you are decelerating---can you hear the knock when decelerating ?(foot off gas from high speed))

No, I do not hear the knock when decelerating. I mostly hear it when I am not moving, but on D or R, and when the car has warmed up some. Temps have been quite low here, low teens, and the knock doesnt appear. Also,iInteresting you mention vacuum, since I was thinking that way as well. Is it a possibility that when the car heats up, that things have expanded and not as tightly efficient as possible? Grasping at straws, yes.....

Any other things to look for to verify the pistons, pins?

Thanks for the response, I know I was a bit late in responding.

[njjuliano]

Sadly, I also suspect it's something to do with the pistons. [One time my M45 sat for about a month. Started her up, and it did throw one hell of a tantrum while starting, complete with a rattling sound...long story short, now It's sitting pretty in the garage with an engine waiting to go in].
The reason I asked about oil consumption initially is that broken rings will let a good amount of oil into the combustion chamber. Add that to the normal oil consumption of our cars (I mean normal in a VK45 kind of way) and it gets pretty noticeable. However, I know you are not experiencing low oil issues. I'd recommend you get codes pulled from your car even if the CEL is not on, just to see if the knock sensor detected anything funky. Also get the compression checked.

We had compression checks early in the life, 30k, and was mentioned normal.

I'll codes pulled, and see where that leads.

I really need to get other ears on it, and ears that know. Even the tests that I want done, Im looking to find a good independent that knows the car. I feel that might get me more info, and more leverage with the dealers to get the situation addressed.