Knocking sounds at certain velocity

[CrazyShini]

Hi all,

lasts weeks I noticed that when I reach 70km/h speed (44mph) or sometimes 90kmh or 110, I can hear a syncronus "knocking" sounds from below. Allways are 3 "knocks" with the same rythm and same sound. These sounds are non perceptibles when you're talking or with music/radio.

I asked to my dealer and says that doesn't know anything about that and never heard about it. Anyone has listened this sounds? Anyone knows its procedence?

Thanks

 

[TonyP]

It could be the valves that open and close to allow the coolant to circulate around the battery. Also check rear springs as I have had one fail on my car.

 

[CrazyShini]

I thought the same about the refrigerant system that maybe activates or deactivates some parts, but for example is strange that allways happens in same velocity (more or less), and if you press the brake pedal, it's stop the synchronus sounds, I mean allways hear 3 knocking sounds with the same rythm, but If I press the brake pedal when you start to hear 1 or 2 of the sounds, it stops and don't hear the rest.

The dealer says that never heard anything about the kind of the cooling system with sounds from there, know about the regulation of MG4, but doesn't know about any regulation here.

Thanks, TonyP. I will check the springs, but I understand that the springs doesn't regulate it's possition or something with the speed, isn't it?

 

[Robf]

I thought the same about the refrigerant system that maybe activates or deactivates some parts, but for example is strange that allways happens in same velocity (more or less), and if you press the brake pedal, it's stop the synchronus sounds, I mean allways hear 3 knocking sounds with the same rythm, but If I press the brake pedal when you start to hear 1 or 2 of the sounds, it stops and don't hear the rest.

The dealer says that never heard anything about the kind of the cooling system with sounds from there, know about the regulation of MG4, but doesn't know about any regulation here.

Thanks, TonyP. I will check the springs, but I understand that the springs doesn't regulate it's possition or something with the speed, isn't it?

Out of left field, could there be a loose hose? perhaps brake given noise disapears when brakes are applied. Or a loose cable? I am meaning under the car, increased wind velocity (speed related) can set of rythmic movement.

 

[DBedford]

Maybe worth checking to ensure nothing is loose under the boot floor.

 

[CrazyShini]

Out of left field, could there be a loose hose? perhaps brake given noise disapears when brakes are applied. Or a loose cable? I am meaning under the car, increased wind velocity (speed related) can set of rythmic movement.

It's very rythmic to be something with de wind, It's seems something more like a contactor or valve connecting as ToniP says.

But for your comments it's seems like only happens on my car, not on yours. Just to give extra info, it's the 2022 ZS EV.

 

[Robf]

It's very rythmic to be something with de wind, It's seems something more like a contactor or valve connecting as ToniP says.

But for your comments it's seems like only happens on my car, not on yours. Just to give extra info, it's the 2022 ZS EV.

Wind has blown down bridges, it just needs the right frequency or velocity, i would check, at least its another thing off the list of possibilities. I think there was a previous post where the brake hose was loose and was rubbing against the wheel it was a MG PHEV but im sure you get the possibility.

Rear washer stopped working - brake system to be stripped to repair

My rear washer water stop a few week ago, taken in to garage today for repair which could not be done by the poor technician who was pulling his hair out. A pipe has come off on the back wall in the engine bay up in the right corner next to the brake servo, from here to the back the pipe runs in...

www.mgevs.com

Scisnack | Winds that huff, puff and blow down bridges

www.scisnack.com

 

[Kithmo]

Could it be the warped undertray flapping ?
Edit: scrub that I thought I was in the MG4 forum.

 

[TonyP]

I can sometimes hear the coolant valve(s) open and close on my ZS EV Trophy, but the noise is not intrusive. The three knocks does sound like it is the coolant valve(s) operating though. Maybe the valve is not restrained properly?

 

[Piperman]

Hi all,

lasts weeks I noticed that when I reach 70km/h speed (44mph) or sometimes 90kmh or 110, I can hear a syncronus "knocking" sounds from below. Allways are 3 "knocks" with the same rythm and same sound. These sounds are non perceptibles when you're talking or with music/radio.

I asked to my dealer and says that doesn't know anything about that and never heard about it. Anyone has listened this sounds? Anyone knows its procedence?

Thanks

It may sound strange, but I something get what sounds like a knock. Buy its from the radio if it's not hat a good signal. I know it sounds strange but when it turn the sound off. The knock dissappear. Just a thought.

 

[CrazyShini]

Well... Don't know how and without do anything, the sound that was hearing during 1-2 months, stopped. I have done nothing to stop it. I supose that it was something with a valve or something, but I'm doing exactly the same as I was doing,... but the sound just has dissapear.

As @TonyP says, the sound is not intrusive, it's just a little sound that you can hear if the radio is Off or you're driving in "relative" silence. If you'r talking or listenning music at certain volume is easy that you don't hear it.

If someone knows about this I really wants to know it too.

 

[tomsl]

I have my MG ZS EV since June and I started to notice this exact sounds. It sounds like it comes from underneath/center of the car and is always very rhytmic: click .... click ... click

It repeats every 3-5 minutes.

I have 4000km on now, and I didn't notice it until very recently. I haven't been on the Autobahn since, so I don't know if this also happens at higher velocity.

Another thing which is unrelated I guess: when I drive around 90km/h and I go off the gas pedal, the motor makes a weird wailing like noise. When the speed drops further it stops. It happens with all 3 KERS settings and in Autopilot. Did anybody experience this as well?

 

[CrazyShini]

I have my MG ZS EV since June and I started to notice this exact sounds. It sounds like it comes from underneath/center of the car and is always very rhytmic: click .... click ... click

It repeats every 3-5 minutes.

I have 4000km on now, and I didn't notice it until very recently. I haven't been on the Autobahn since, so I don't know if this also happens at higher velocity.

Another thing which is unrelated I guess: when I drive around 90km/h and I go off the gas pedal, the motor makes a weird wailing like noise. When the speed drops further it stops. It happens with all 3 KERS settings and in Autopilot. Did anybody experience this as well?

It's exactly that!

Appears one day, with no apparent reason, and you live with this X days. In my case it happens when pass trhough 68km/h to 70km/h (more or less), and again at 90km/h, 110,... If I drive at 65km/h, will never happen.
Always happen when you're accelerating (no matter the power), and if you start to hear the sound and then stops the acceleration, it cancels the rythm. I mean, If you are accelerating and hears the first "click" and release the pedal, you will not hear the second and third "click".
I have to say that this sounds dissapear to me with no reason (just as it came) and now didn't heard again since 1 month ago.

About this other sound that you say. You told that you're in Autopilot (cruise control?), and then release the pedal? Like if you set 85km/h on the Autopilot and you push the pedal to arrive at 92 and release then?
I think that in my ZS (and I thought all), the Kers didn't works on Autopilot. When I find a slowly car in front on me and the car start to decrease velocity, I see no regenerative power on the screen. I suposed that the Kers doesn't work with that option unlike MG4 for example.

 

[tomsl]

Weird... since it is so rythmic, almost like one knock per second for 3 seconds, I don't think that wind or loose bolts are the cause. Yesterday I didn't hear it at all, the day before every 5 minutes.

The other thing: my conclusion was that it isn't related to KERS, that's why I mentioned the ACC, because to my knowlege it doesn't use KERS (pitty).
It's a bit difficult to describe because English is not my first language nor do I know anythng about car things and motors. But it is like if the motor is at a certain stage, this typical buzzing sound becomes "wailing" for a short period of time. That's the best description I can come up with:
zzzzzzWOWOWOWOzzzzzzzzzzz

 

[Gadget Geek]

It sounds like frequency resonance. When you hit a certain speed, various components of the car can start to vibrate in synchrony with the vibration caused by the wheels rolling on the road.

 

[tomsl]

@Gadget Geek I guess you are refering to the motor noise? I think I'm gonna open a separate thread, otherwise this will get mixed up with the original topic (knocking sounds).

 

[Gadget Geek]

@Gadget Geek I guess you are refering to the motor noise? I think I'm gonna open a separate thread, otherwise this will get mixed up with the original topic (knocking sounds).

No. Any inert component in the car (body panels, windows, etc) can act like a tuning fork when the correct frequency is reached. As the sound occurs at certain speeds, this suggests that at those speeds, the whole car will be vibrating at a given frequency. If, say a window, is in phase with that vibration, it will start to vibrate in sympathy. If you can narrow down where the clicking is coming from in the car, you might find something needs tightening or needs some dampening material to stop the vibration.

This video explains it better than I do;


It's just a theory to explain the specific speeds at which the clicking occurs. I might be totally wrong.

 

[Alan]

I hear a sound that to me sounds like an electrical relay, that is 3 'knocks', haven't noticed it at any particular speed though I also had it on my previous MK1 ZS EV. I hear it every now and then. I almost never have music or the radio playing which may be why other people haven't noticed it and I have?

 

[scoobeesnac]

I have also just started to notice this since the car was with MG, I wondered if it was a water bottle as it was so rhythmic but it's quite a strong tap-tap-tap sound coming from near the cup holders.

 

[tomsl]

So today my wife was sitting in the back with our son and she noticed the clicking sound as well. She said it comes from behind, so basically the trunk.