Diesel Sound?

[Micko1]

I’ve only had the NC a couple of weeks so still getting used to the sounds but today I noticed that it sounds rattly, like a diesel engine, at around 1500 revs while accelerating. It quickly disappears but it’s noticeable when it’s there. I also notice it when driving slowly in traffic in 2nd, again at around 1500.
Is this normal for these cars.

[ckleanth]

Have a read at this, there are plenty of suggestions.

more info here

Nc engine knocking noise. What say you?

I have a bit of a dilemma. I just noticed a weird knocking noise and not sure its the stupid noise producing solenoid that i disconnected or its the flipping engine piston rods. It comes from the solenoid side but unsure… any ideas? Edit, oil levels ok (above the second hole on the dip stick) Noise filmed from the inside [nc engine knocking noise inside] Noise filmed from the outside [nc engine knocking noise outside]

[Micko1]

Thanks. That’s not the noise I’m getting though.

[Jimbo_Ittai]

Its backlash in the gearbox. Dont worry a lot of them do it. Of course that assumes you’ve still got oil in your gearbox but im sure you likely have.
Im sure there was a thread about the low-rev diesel sound from an NC gearbox a year or so back.

[Micko1]

Thanks. I had a look but couldn’t find anything on the type of sound I was getting. But, if anyone has a link to that old topic, I’d certainly appreciate it. Thanks folks

[Jimbo_Ittai]

NC 3.5 annoying gearbox noise under load low speed

Hi all, I am getting an annoying noise from the gearbox when under load at low speed in all 6 gears. but especially noticeable in the lower gears due to lack of road noise. Someone has suggested that it is due to the transmission height not being correct where is joined to the support ladder that connects to the differential, does this sound correct? It does not sound like a bearing failing so just wondered it this sounds correct and if anyone knows what the correct height should be? Many than…

Here it is FYI

[bally3]

I’d be checking serpentine belt and pulleys 🫣

[Jimbo_Ittai]

Yes I’d def do these checks as well to rule out problems with worn bearings etc.
I read a fair bit on other forums about this gravelly diesel sound on NCs at low revs under load. It seems to be a regular experience for owners of these cars. I would of course defer to any technical input by someone who knows more than me. My car does the exact same and has had gearbox oil changed twice. I think it is just a feature of the car assuming all other things are ruled out.

[Micko1]

That link describes exactly what I’m hearing. I’ll happily live with it if it’s just a feature of the model. Had a service in January when gearbox oil was changed so I’m not too worried about oil level. No point in me checking belts and pulleys as I wouldn’t know where to start . Guess I’ll monitor for now. Thanks

[Keat63]

Belt tensioner is not unknown to fail.
I heard one at work with a strnage knocking noise, informed the owner, and it turned out to be exactly that.
Only at low revs though.

[Micko1]

Thank you. Mine is not a knocking noise. It’s almost exactly what was described in that old thread.

[Jimbo_Ittai]

Diesel-sounding MX-5 - MX-5 Miata Forum

Here’s what the Americans have said on the issue of NC gear lash or rattling/metallic noise at low revs under load. There’s plenty more info on the subject via Google. If your car idles quietly without squeaks knocks and rattles but makes this noise accelerating or decelerating at low rpm and speed it’s more than likely this common trait which my car also has. It can sometimes be a noisy clutch release bearing, if the noise goes away when the clutch is pressed when stationary it might be this. My car has both of these little traits and I don’t worry about it. These cars are meant to be driven not laboured in 6th gear at low rpm so I try and transit this low rev regime as swiftly as possible👍