Audible Knocking above 3K RPM's
 

I'm totally clueless on what is causing this knocking sound.

Here a little info about my Car

2005 G35. Rev-Up Motor
Greddy 18G twins installed Sept 2009
Import Parts Pro Stage 1 block installed Sept 2009
Stock Head with about 20K miles on them
HKS FCON VPro tuned but Forged

The car had 55K miles when the twins and block was installed. I'm about to hit 60K miles, and within 5K miles I did 3 oil changes. The first change within 30 miles, the 2nd oil change after 1k miles, the 3rd change 2K miles from the last change. Since I'm breaking in the motor I using 10W-40 Castrol GTX. I'm about to switch to AMSoil next month.

Ever since I leave Forged, the car has been solid. The only problem I had so far is a little exhaust leak coming from a loose bolt on the exhaust manifold. Well tonight I started up my car, and let it run for about 4 minutes to warm up the engine. As I was leaving my neighborhood I noticed a loud Knocking coming from the engine bay as I started to Rev pass 3K RPM's. I pulled over to a parking lot down the road and poped my hood to see if anything was loose, nothing. I asked my friend to Rev, and again I could hear a loud knocking coming from the engine. So I drove back home and let the car sit for 30 min and checked the oil. The oil level is fine, just below the "H".

The last 2 times I drove the car is was fine. Friday I drove from work to home (about a 30 min drive), and yesterday, a quick run to the store.

Another factor is the cold weather, Its been about 32 or colder all day.


Any thoughts?

Is there any way for you to get some vids up so we can hear it?

+111 let's hear it...

was it a knocking or a ticking? I had a massive exhaust leak from a blown exhaust manifold gasket and it would only get loud when the engine was cold. After about 10 min of driving it would go away until the gasket completely blew out

When it warms up, does the sound diminish? Is a deep hollow knocking noise, or a ticking noise?

Did you ever fix the exhaust leak? A small leak can sound like a pop if its coming from the flange. My car runs like ass in the morning until it warms up thanks to the expansion properties of forged pistons vs the cylinder liners.

Hey Sharif

There is no knocking sound at when I warm up the car or idling. Only under load. It sound like a woodpecker.

Ok, Here a quick video.

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No, I was waiting under my 60K service which I'll be doing next week. The reason is that the loose nut is on the Drivers side exhaust manifold, right in front on the compression housing on the turbo. Meaning I need to drop the turbo to get to the bolt.

Wow that is loud, almost sounds like exhaust hitting the body, or the engine rubbing something, piping perhaps?

On my sh!tty laptop speakers, it sounds like a spun bearing, but I'm hoping that's not the case.

Thats what I was thinking.....eeeeekkkk..

drain the oil and pull the pan and see if you can tell anything from underneath.

Tom

Nope that doesn't sound like exhaust.

Listened to this with my 5.1 surround setup and it reminds me of an exhaust leak one of my cars had, the entire exhaust manifold was never tightened on one side of the motor by the guy I had put the motor in , but this actually sounds worse, good luck to you with finding the cause!

Oil Pressure normal ?

Can you have a friend pin-point or narrow down the noise origin while you increase the engine RPMs ?

does it still make the noise when you just rev it in neutral? or is it only under load?

tom

i agree but if it was a spun bearing he would hear it at idle as well not just above a certain rpm range.

Def not knock because your motor would have torn a rod just in the time it took you to shoot that vid.

Another thing i thought of is to take the upper and lower plenum off. Look down the runners and check the valves. Also if some one had a camera scope you could look down the spark plug holes and make sure the pistons look ok.

Hard to tell what it is from the video but def could be something simple.



If it was me i would do like what was already mentioned and drain the oil into a pan with a cloth filter of some sort to catch any metal shavings.


Good luck.

Doesnt sound good at all. I would drain oil and check for metal...pull lower pan.

Not true at all. I spun a bearing in my z31 turbo forever ago....drove on the spun bearing for about 300 miles before getting motor replaced.

keeping fingers crossed for ya, but check oil, pull pan and see what ya got

Tom

This is what I suggest you do. Make a mechanics stethoscope, listen to each side of the engine at idle when it is making the noise, and have someone rev the car slowly when your under the hood and listen to where it comes from. Also if you could make another video at idle it would help. I took the bass out of my speakers and it could possibly be an exhaust leak at the manifold. Mine did sound similar to that when i had a blown header gasket. The video inside the car is going to muffle the sound to make a good video diagnoses. I went through 3 aftermarket gaskets until i went to nissan and bought an oem one, learned my lesson.

my exhaust manifold on my daily cracked straight down the middle and NEVER sounded like that. I dont know what kinda exhaust leaks you guys are used to.

Citymunky are you ever gonna let us know what you found.