There have been a few posts about engine knock noise of various sorts...
And nobody seems to have figured it out yet...

WHAT:
knocking noise from engine, also heard in passenger cabin, only when warmed up idle. Hard to hear it when AC or engine cooling is running.
Can be sometimes pretty loud, sometimes very faint.
I would not call it a clicking or pinging noise, more a banging or knocking noise. May remind some of how a tractor sounds (tock a tock a tock a tock).
Goes faster when reving.. knocks distinctly audible at lowest (idle) rpm with a few knocks per second, with revving to higher rpm knocks no longer discernible..

NOTE: car seems to run just fine, so far it seems a noise problem only (at least I hope so)

INFO FROM WIKI ABOUT FUEL DAMPERS:
Similar to "water pipe banging" in old buildings related to water pressure changes, fuel damper has something to do with regulating fuel pressure and could cause such noises...

WHAT THE NISSAN TECH @ dealership SAID:
does not sound rhythmic, hence no serious engine problem
Guessed fuel damper, looked up TSBs, found it, and agreed to replace.

UPDATE
Knock remained unchanged after TSB was performed.
Dealer then replaced the 2nd fuel damper on the rear side of the engine (which is not the one in the TSB).
Unfortunately no change again...

Anyone any ideas?

VIDEO:
Click here to watch 350z-engine-knocking-

 

sounds rhythmic to me...

 

I got the same exact problem....thought it was only me. it's a rythmic knocking while idling, cannot hear it when fans or ac on. can hear it loud and clear, specially on quiet night with radio off. what could it be...??? sounds like a Diesel engine

 

sounds pretty rythmic to me. It could be piston slap. its when the piston is too small for the bore (usually in performance engines) and the piston skirt slaps the side of the bore because of the two points of rotaion the wrist pin and the crankshaft the piston has to go straight up the bore while the rod tries to push it hard into the outer wall of the bore. The manufacturer usually puts a teflon coating on the piston skirt to dampen the noise.

Sorry if thats to technical, but it is a possibility.

 

i have the same thing also, for over 9,000 miles. i just hope its nothing serious, nissan said its nothing but i don't trust them. i'm also afraid to ever put FI on the motor now too : (

 

piston slap sounds interesting... It sure sounds like something slapping inside the engine... hopefully this is really normal and just a noise... and no extra wear on engine parts...

Thanks for the feedback...

I guess not worth it to pursue further?
Or are there any simple tests the dealership could do to look into it?
I have heard about compression tests, and checking each cylinder, and all sorts of things, but I have no understanding of engines to know whether any of those would make sense in this case.

 

there really isnt a good test for piston slap, other than tearing the engine apart and measuring the piston skirts and bores. A compression test will show good numbers because the rings seal the bore, not the skirt. It is more annoying than anything else, it isnt going to destroy your engine. Most race engines have piston slap when they are started and think about the punishment they go through

 

what else could it be?

 

Any Updates on this issue????

 

Hi, I posted the following this morning....sounds very similar..

03 with 25,000 miles driven on week-ends...Driving home yesterday 1 mile from home I heard a loud clanking noise. Pull into garage and turn off the car, check oil and there is oil on stick at the "H" mark. Start car up and noise starts...standing in front of engine noise comes from a location near the firewall towards the rear of the engine...Plan to tow to dealer on Monday....

 

*Update*

A big thank you to OverZealous1, a true car enthusiast and great guy who offered to listen to my engine using his stethoscope. I was lucky to be local, and lucky that he found time.

While everyone here might have a different problem, in my case it seems like one of the valve lifter caps being a little out of spec (too loose) and therebey creating this noise.
One can obviously not be certain without taking things apart.
As far as I understood, it isn't a big problem, even if the valve cap gets totally ruined, it is fairly easy to repair and shouldn't cost too much.
Ok to drive like this, and look into it if the noise gets worse.

Personally, I am not sure if it is a good idea to let the dealership open up the engine... So I will wait and see if it gets much louder.

Actually there are a few posts about valve tapping and noises on this forum as well.

Please everyone post any updates if you find out more, or get it fixed somehow...
Thanks

 

I had a similar sound on my G35. It puzzled me for a week. Turned out that it was the vacuum line going to the fuel damper on the rear / passenger side of engine. The line looked fine from the front but was hard and cracked around the back.

Hope this helps some one.

Dave

 

any other updates on this? i just heard my today and now its bugging the crap out of me.

 

I ended up having the engine replaced; insurance paid for it almost immediately which made the fight with the dealership mute. The noise was very, very, very loud. As noted I had thought about having someone look at the engine however by that time the car had been at the dealership for 1 1/2 weeks.

Really appreciate you guys being there and offering suggestions or thoughts. She's been back on the road (still only on week-ends) and "holding court" nicely. Z ya

 

HAve you guys done a search on the Loud knocking Z Clutch? If you guys have M/T its your clutch making all the noises you hearing. Try pushing in your clutch and let out in gear a bit. It will quiet down for alittle while. Never know, it may be your motor.

 

its not the clutch. we know about the clutch noise. This noise is killing me.

 

During a tech inspection another shop listened to this noise and they also lifted the car up.

As the noise seems louder from the bottom they don't think it is related to the valves and they think I should bring it to the dealership again.

The knock has become a regular noise now and is always there when warmed up. It is getting louder.

The noise is there regardless of clutch in or out.

Anyone else has any news on this?
I am getting PMs, seems like there are many people out there with that problem.

Noticed a new TSB "low oil level and unusual engine noise" ntb07-088b but I cannot look at it as nissanhelp limits your downloads to 1 file per day which is outrageous.

 

I have this same EXACT problem...

-Only happens when warm
-happens only at idle or fast idle
-Sounds like the noise previously descriped above as a thunking.

-The concensus seems to be that it is the fuel dampers. Does anyone have a pic of where these are located in the engine. I guess I could follow the fuel rail and find out. Is it simply the vacuum line going to them that causes the issue or do the units themselves go bad? What would be the replacement costs? Sorry for the questions but I'm trying to sell my Z and this is the issue I need to resolve to sell it.

 

I'll post pics of the fuel dampers when I get into the engine this weekend. hopefully it is a pretty straight forward fix.

 

I also have this noise. I suspect it could be the Dual Mass Flywheel (Assuming we all have 6sp manuals).

The other thin i have noticed that if i bring the car speed down so i am doing about 1200-1500rpm in say 4th of 5th gear then i can feel what appears to be the same rythmic knock through the clutch pedal. Don't push the clutch right in just take up the load a bit thorugh your leg. Try this, i would be intrested to see if you have the same.

Try doing a few searches on Dual Mass Flywheel problems on the net. Other cars that have what seem to be similair symptoms are Mini's, BMW's, Porsches and Vettes. Most new or expensive cars that have 6sp trannys have a DMF to reduce noise and vibration into the cabin when driving at low rpm in higher gears.

When they begin to wear out the springs can weaken allowing the "two" flywheels to knock into each other and creating all kinds of bad noises.

Let me know your thoughts. I tried to get nissan to check this in my car but they don't beleive that it could be the cause despite not being able to diagnose it themselves!

Regards,

Rusty