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Discussion Starter #1 (Edited)
Hi everyone. Recently got myself new Mazda 3 HB G122 petrol (Europe, made in Japan). Car is great all around, but this knocking sound from engine bay worries me. My old Mazda 2 sounded perfect.

It can be heard from outside of the car when the engine is warmed up and idle. Knocking is not that loud, it's intermittent, not rythmic with the engine and noticable. It's hard to pinpoint where it's coming from, seem a bit louder from the passenger side. All appears and sounds normal when driving. Anyone else noticed this? What could it be?

Tried to record it, best heard at around 0:15
 

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Can it be M-Hybrid's Generator which starts/stops charging the 24V battery? Is it possible for you to check this via the energy flow monitor on your infotainment screen?

During idling, M-Hybrid's Generator engages/disengages roughly once in a minute or so...
 

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Discussion Starter #3
I'll check, but I don't think so. This knocking or ticking sound is always there when the car (engine?) is warmed up, just at irregular intervals, something like this: tick-tick---tick--tick----tick-tick-tick---tick----tick-tick--tick.

I noticed it just because I have to exit the car to manually open and close my home gates- when leaving and when engine is still cold it sounds fine, no ticking. Knocking or ticking is always there when I return home and car is at working temperature.
 

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I'll check, but I don't think so. This knocking or ticking sound is always there when the car (engine?) is warmed up, just at irregular intervals, something like this: tick-tick---tick--tick----tick-tick-tick---tick----tick-tick--tick.

I noticed it just because I have to exit the car to manually open and close my home gates- when leaving and when engine is still cold it sounds fine, no ticking. Knocking or ticking is always there when I return home and car is at working temperature.
Have checked your video one more time. I have the Skyactiv-X and it sounds like that also during idling.
 

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Discussion Starter #5
Thanks for that. It might be just normal operating sound, it's just a bit weird, like two marbles randomly knocking into each other.
 

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Thanks for that. It might be just normal operating sound, it's just a bit weird, like two marbles randomly knocking into each other.
I have done some further research on what possibly may make this ticking/clicking noise. Without confirming this on my vehicle, I have found that this may come from AC system's dehumidifier (which is obviously working harder during colder days, this noise comes from the normal operation of it). If you want to confirm this, please listen to the engine one more time with the AC completely switched off.
 

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Discussion Starter #9
AC system was always off, only normal ventilation system was operational. I'll try with AC on and ventilation off.

Like brassrox said, I also found some information that this is sound from fuel injectors. Also, might be that injectors produce this sound due to low outside temperature. My Mazda 2 also has direct injection engine (1.5 petrol 90 HP), but never heard any knocking from that engine, no matter the AC, temperature, fuel quality etc.- that was puzzling me.
 

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AC system was always off, only normal ventilation system was operational. I'll try with AC on and ventilation off.

Like brassrox said, I also found some information that this is sound from fuel injectors. Also, might be that injectors produce this sound due to low outside temperature. My Mazda 2 also has direct injection engine (1.5 petrol 90 HP), but never heard any knocking from that engine, no matter the AC, temperature, fuel quality etc.- that was puzzling me.
Just wondering/make sure, does "only normal ventilation system" include blowing on the windshield? On mine, the blow on windshield turns on AC (without the AC light). Did you still hear with ventilation system completely turned off?
 

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Discussion Starter #11 (Edited)
Just went for a drive, I'll write few observations, some will answer repiles above:

-ticking present at idle, 500 RPM, with "normal" ventilation on, off, blowing on windshield (without AC), blowing any other direction.
EDIT: I am aware of that function that blowing on windshield turns AC on, Mazda 2 does that and turns AC light on. On Mazda 3, light remains off and RPM stays at 500, also compressor stays quiet so I'm not sure
-ticking goes away when car starts to charge the M-hybrid battery (Energy flow monitor displays this), during this time RPM goes up to 600-650. After RPM falls back to 500, ticking gradually comes back and becomes more audible.
-ticking goes away with AC on as this also makes engine RPM go slightly higher

Regarding the M-hybrid charging and AC on situations, I think the ticking goes away, engine and other systems are a bit louder in these situations so it's difficult to tell.

My guess is the ticking is present only at idle at 500 RPM, or I assume the lowest possible RPM.

And man, that ticking can go wild (in rythm, not volume, it's never very loud). Today, one second it ticked 5 times, the next second 1 tick, then next second 3 ticks and also can be quiet for some seconds. So weird.
 

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Just went for a drive, I'll write few observations, some will answer repiles above:

-ticking present at idle, 500 RPM, with "normal" ventilation on, off, blowing on windshield, blowing any other direction
-ticking goes away when car starts to charge the M-hybrid battery (Energy flow monitor displays this), during this time RPM goes up to 600-650. After RPM falls back to 500, ticking gradually comes back and becomes more audible.
-ticking goes away with AC on as this also makes engine RPM go slightly higher

Regarding the M-hybrid charging and AC on situations, I think the ticking goes away, engine and other systems are a bit louder in these situations so it's difficult to tell.

My guess is the ticking is present only at idle at 500 RPM, or I assume the lowest possible RPM.

And man, that ticking can go wild (in rythm, not volume it's never very loud). Today, one second it ticked 5 times, the next second 1 tick, then next second 3 ticks and also can be quiet for some seconds. So weird.
That rules out the AC (I think).

Speaking from experience (from another car, not the Mazda 3), I have a "similar" issue (as with other owners via that forum), though not quite "tick" but between a "tick" and a "clack". They are "somewhat rhymic" -- e.g. 5 times, then somethings 10, then sometimes 2, etc., and more on hot weather. It was related to the starter-generator/alternator.

With that, I would guess (again, only a guess, not definitive or anything) it may well be related to starter-generator/alternator and in the the M-hybrid set up it's all integrated into one unit (the ISG).
 

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Discussion Starter #13
That rules out the AC (I think).

Speaking from experience (from another car, not the Mazda 3), I have a "similar" issue (as with other owners via that forum), though not quite "tick" but between a "tick" and a "clack". They are "somewhat rhymic" -- e.g. 5 times, then somethings 10, then sometimes 2, etc., and more on hot weather. It was related to the .

With that, I would guess (again, only a guess, not definitive or anything) it may well be related to starter-generator/alternator and in the the M-hybrid set up it's all integrated into one unit (the ISG).
Next time, I'll just leave normal ventilation on front to completely rule out AC and dehumidifier. I was switching it on and off every few minutes, maybe that's not the best way to do it.

The sound can be described as "clack" also i guess, and it is "somewhat rhythmic". Something like "tk" would be most accurate in my language.

You wrote "It was related to the .", is something missing here?
 

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Next time, I'll just leave normal ventilation on front to completely rule out AC and dehumidifier. I was switching it on and off every few minutes, maybe that's not the best way to do it.

The sound can be described as "clack" also i guess, and it is "somewhat rhythmic". Something like "tk" would be most accurate in my language.

You wrote "It was related to the .", is something missing here?
It was supposed to be "It was related to the starter-generator/alternator" -- I had hit cut instead of copy -- thanks for pointing it out! Corrected.
 

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Discussion Starter #15
It was supposed to be "It was related to the starter-generator/alternator" -- I had hit cut instead of copy -- thanks for pointing it out! Corrected.
No problem. Starter-generator would explain why Mazda 2 sounds "normal" (as my model is not equiped with M-hybrid system) and also why HCCI thinks his Skyactiv X has the same sound (I would assume it's the same unit for all engines). Also, looking at Mazda promotional material, generator is located on the right, passenger side where I believe the sound is more prominent.

During my quest of googling this issue, I found some suggestions to improvise a stethoscope and try to pinpoint source that way. I'll try that.
 

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AC system was always off, only normal ventilation system was operational. I'll try with AC on and ventilation off.

Like brassrox said, I also found some information that this is sound from fuel injectors. Also, might be that injectors produce this sound due to low outside temperature. My Mazda 2 also has direct injection engine (1.5 petrol 90 HP), but never heard any knocking from that engine, no matter the AC, temperature, fuel quality etc.- that was puzzling me.
Actually I have caused a misunderstanding, sorry for that, what I meant was to turn of the entire climate control system. You may try turning it off entirely and listen to the engine.

EDIT: I have missed the part of your comment where you have stated that you tried with the climate control completely off so you may try what I have written below:

By the way, do you have a manual gearbox? If so, do you think that you may get a help from another person to depress the clutch while you listen to the engine outside in front of the car? If you are unable to get help, it is no problem, the thing in my mind is not a very likely reason for this type of ticking.
 

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Discussion Starter #17 (Edited)
Today I turned off ventilation and AC completely during the rive and ticking was again present at idle.

Yes, it's manual and I already tried that- ticking continued with depressed clutch. I did it myself as I can hear the clicking with driver's door open.

My mother has classic medical pressure gauge so i borrowed the stethoscope LOL, I looked ridicilous but I tried to listen to various parts that are reachable and I could not pinpoint the source of ticking, all I could hear were mechanical sounds from the engine. Engine seems to run fine, nothing from high pressure fuel pump and some other parts that I do not know names of. Now, either all reachable parts are not the source of clicking or the engine sound just overwhelms the clicking.

There is slight possibility that I could hear some faint clicking from the integrated starter generator, but I'm just not sure. I imagined the real source would have very obvious clicking sound in my ears.

Sometimes I would think the sound is coming from somewhere behind the engine, where the exaust manifold is, but it might be just my mind playing tricks on from this point.

And yes, I thought to myself, this is just insane what I'm doing. Of course, I could just go to my dealer and let them check it out, but I'm 100% sure they would just say it's all great.

On the positive side, some of the sounds from the engine were just amazing to hear this way.
 

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Today I turned off ventilation and AC completely during the rive and ticking was again present at idle.

Yes, it's manual and I already tried that- ticking continued with depressed clutch. I did it myself as I can hear the clicking with driver's door open.

My mother has classic medical pressure gauge so i borrowed the stethoscope LOL, I looked ridicilous but I tried to listen to various parts that are reachable and I could not pinpoint the source of ticking, all I could hear were mechanical sounds from the engine. Engine seems to run fine, nothing from high pressure fuel pump and some other parts that I do not know names of. Now, either all reachable parts are not the source of clicking or the engine sound just overwhelms the clicking.

There is slight possibility that I could hear some faint clicking from the integrated starter generator, but I'm just not sure. I imagined the real source would have very obvious clicking sound in my ears.

Sometimes I would think the sound is coming from somewhere behind the engine, where the exaust manifold is, but it might be just my mind playing tricks on from this point.

And yes, I thought to myself, this is just insane what I'm doing. Of course, I could just go to my dealer and let them check it out, but I'm 100% sure they would just say it's all great.

On the positive side, some of the sounds from the engine were just amazing to hear this way.
Cool!

Well, at least engine seems to be fine...I guess as long as it's not engine knock then hopefully it's a non urgent minor nuisance.

Maybe some bolt is loose?

Sent from my HD1905 using Tapatalk
 

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Discussion Starter #19
Cool!

Well, at least engine seems to be fine...I guess as long as it's not engine knock then hopefully it's a non urgent minor nuisance.

Maybe some bolt is loose?

Sent from my HD1905 using Tapatalk
I don't know, it could be. Today I ruled out fuel, after two full tanks of 100 octane fuel ticking remains. So yeah, I guess it's not engine knock.
 

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I don't know, it could be. Today I ruled out fuel, after two full tanks of 100 octane fuel ticking remains. So yeah, I guess it's not engine knock.
At such a low load like idle and with a lot of electronics designed to protect, engine knock is very unlikely. Please do not worry about it...
 
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