ND2 (184 bhp) Knocking/Tapping Noise When Cold

Technical Area Engine, Transmission, Exhaust etc
2

There is knocking/tapping sound from my 2.0 litre ND2 when cold which seems to be much louder than anything I heard on my 2.0 litre ND1 when it was cold. If it was making such a noise when hot I would suspect a tappet clearance problem or a broken piston ring.  It does go away when the engine is fully warmed up though i.e.at 90 degC. Has anybody else noticed this and is it because of the differences  (clearances etc) between the two engines? I would appreciate your thoughts/observations.

3

Mine’s noisy when starting but only for about 10 seconds - apparently, I have been told, it’s whilst the cat warms up and the engine management system adjusts the timing.

Some owners in the U.S.A. start their cars from cold with the reverse gear selected (declutched, of course) and maintain that this bypasses the cold start routine the engine management system invokes.  I tried it and it didn’t seem to make or sound any different.

From the Manual Section 4-6 in mine - “After starting a cold engine, the engine speed increases and a whining sound from the engine compartment can be heard.
This is for improved exhaust gas purification and does not indicate defect of the parts.”

Again, from a U.S. site . . . .

Do the reverse trick to bypass the warm up blather.

1. handbrake up
2 clutch in and reverse gear. hold clutch in do not touch brake or gas pedal.
3. start button.
4. don’t touch any pedals for the next 20 seconds or so and leave it in reverse.
5. done

Hope this helps . . . 

4

Hi Jeff,

Thanks for your reply and your research which is appreciated. I am familiar with the Emission Control system produced noise, which as you say last for about ten seconds or so and is no different to my ND1. The noise I am describing is a much more metallic tapping/light knocking noise coming from the engine which does not go away until the engine  is fully up to normal operating temperature (90 deg C).

As to the “reverse trick to bypass the warm up blather” I really don’t see the point of doing that. 

Cheers.

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I only see the point in taking it back to the dealer as it is under warrany!!!

6

Yup.  My heart would be sinking at the thought of being jerked around by the dealer (“they all do that”, “it will settle down when it beds in”, “we can put it on the diagnostic machine but if there’s no fault found we’ll charge you ÂŁ75” et cetera) but I think that’s the first option. 

Or you might of course have a good dealer!

 

7

Interesting Topic ref start-up noises ; Normal and not so.
Having just bought an ND2 (in Eternal Blue coincidentaly) and still learning about it.
Will pay more attention next start up .

Good luck with your unusual noise.

8

Hi Team

I had a ND1 and now have an ND2 both have made identical noise on start up,just like one of the tappets is slightly out of adjustment,but goes away very quickly once slightly warm,i asume it is basically just that,the last car i did about 23000 miles in and it never changed in all that time,this car i have done 8000 miles in and still is doing it,but it does not worry me at all,obv i have the three year warrantry,and i hope to sell it for another one in about 18 months hopefyully for an NE,lovely car so pleased with it,totally different in lots of ways to the ND1.

 

All best Simon

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Guys,

Thanks for all your responses.

Drumtochty, as JohnM says, it will probably be a waste of time taking it to my local dealer at this point as it is very unlikely that they will start it up from cold with me there to identify the noise that I am concerned about. They will probably fob me off, particularly as I did not buy the car from them. As Limon says, it sounds like a tappet out of adjustment. Maybe the noise is louder and continues for longer compared to my ND1 due to a vagaries in manufacturing tolerances (or maybe I am just being paranoid?). What I will do is start the car from cold and try the old fashioned large screwdriver “stethoscope” trick to see if the noise is coming from one particular cylinder or one area of the camshafts etc (when it bloody stops raining!).

If there is a real fault, it has another two and a half years yet of warranty to make itself more apparent and more obvious to a dealer. 

Alloyboy (and anybody else), I would be interested to have your opinions of the tapping noise (or no tapping noise) when you start your cars from cold and how quickly it goes away.

Cheers.

1 Like
10

My Mazda3 has the earlier Skyactive G engine, and it too has the tappety/knock noise on start-up, but it does go away.  It unsettled me to begin with, but then I read up on the technology and discovered the engine adjusts its running mode to suit the conditions, in some instances it is almost a diesel, and I’m guessing that is when it has the loudest knocking sound.  See also “Miller cycle”, a departure from normal internal combustion, something similar is made possible in Skyactive by playing around with the timing of valves, spark and fuel injection.

https://www.mazda.com/en/innovation/technology/skyactiv/skyactiv-g/

https://www.insidemazda.co.uk/2017/11/07/an-in-depth-look-at-mazdas-skyactiv-x-technology/

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Absolutely fascinating Richard. It does beg the question though, if you start modifying things (such as changing exhaust manifolds) does it â– â– â– â– â– â–  up Mazda’s original  design intent unless the ECU is also reprogrammed to maintain as much of the original design intent as possible?

Regarding the noise I am investigating, I have done the screwdriver stethoscope trick and it does seem to be originating from what looks like a roughly 10mm diameter stainless steel tube that runs along the cylinder head underneath the plastic inlet manifold. Is this the fuel injection rail and could an injector be making the noise?

Cheers.

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I expect changing the exhaust manifold will not cause a problem, PROVIDED the branch lengths are maintained at greater than Mazda’s magic “600mm”. They’ve curled them up to keep the heat in and also fit a pre-cat in the space, even on the Mazda3 where there is a lot of room to spare (V8 anyone?).

It is not new technology.  The 4-2-1 exhaust manifold for my old tuned Kent engine had branches of about two feet before the first joins, and that was designed fifty years ago, and it had enormous torque over the whole rev range, much better than the standard manifold.

That stainless tube is the fuel distributor, and it sits on the fuel injectors.  They can be noisy in operation (sounds like clicking), but they are also the seat of the bang when it fires, thus the loudest place inside the cylinder.

I think you are hearing the engine working normally, and when cold it is richer AND at low revs with more diesel-like operation, so therefore louder.  But without hearing it myself, this is still speculation.

 

EDIT.

Bear in mind that is a very, very high pressure fuel injection system with a high pressure pump mounted on the engine as well as the normal pump in the fuel tank.  The injectors and distribution tube have a very complicated seal system, not to be disturbed because it requires all new seals and special tools to reassemble. 

Fuel pressure in the tube varies from about 3MPa (435psi) warm idling to at least 15MPa (2176psi) above 3000rpm!  “During a cold engine start the pressure is raised to promote fuel atomisation.”

 

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Hi Richard.

Thanks again. Agree with what you are saying re exhaust manifolds. Would a 4 to 1 (which I have seen) also produce the same effect? I see that the 4 to 2 to 1 manifolds are paired so that the exiting exhaust from one does not interfere with the other cylinder and allow hot exhaust gas to remain. Anyway thanks for your advice on the fuel injector rail. The other question that might be relevant is whether the ND2 engine is higher compression than the ND1 which might result in the dieseling for a bit longer than in the ND1. 

Cheers.

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Hi did you ever discover what the noise was ?did you discover if it was normal?

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Hi. It did not get any worse and noting other peoples experiences I have come to the conclusion that it is normal. The ND2 2.0L engine is significantly different to the ND1 2.0L engine which may be the reason for the different sound when cold. The engine does make a tapping/knocking noise when cold right up to the point that it has warmed up to normal operating temperature. It is then significantly quieter.

1 Like
16

Mine does it for about a minute or so on cold start was very worried once started completely quiet ,now looking for a 30th anniversary model orange