CX-9 2018 GT Knock noise when using active cruise control

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Mazda CX-9 GT 2018 White
Hi guys,

Today I turned the radio off and I noticed a 'knocking' noise everytime I resumed from hold while using the active cruise control. I'll try to upload a video later but, anyone has this issue? Is it normal? Never hear it before. This is a Cx-9 2018 GT.
 
Mine often makes a very slight "Break Pedal" sound...

(Exactly the same (slight) sound that you sometimes hear when you manually apply (or release) your brake pedal.
 
Well in my case it*s a single knock sound just after the break is released by the system when you press Resume or when it accelerates by itself. It does it everytime. Something is knocking some metallic area or part.
 
I tested it today - everything turned off so very quiet in the vehicle, and yes there is a single "Knock sound" (I do not think that phrase exactly describes the sound, but I do not have a better choice of words to describe it).

Anyway my point is - I also tested manual braking and found when I release the brake manually, (After holding down the brake pedal at a red light and then lifting my foot off of the brake pedal) I hear the same sound!

Try it and see if that is not so.
 
I took it to the dealer yesterday and they told it is normal. The technician said that it is a normal noise coming from the relays and other components related to the MRCC. Don't know if BS or not. My previous Mazda 6 2014 with the MRCC feature never made those noises whe accelerating by itself. Can anybody else verify this noise when using the MRCC?
 
Hi guys,

Today I turned the radio off and I noticed a 'knocking' noise everytime I resumed from hold while using the active cruise control. I'll try to upload a video later but, anyone has this issue? Is it normal? Never hear it before. This is a Cx-9 2018 GT.

It would be nice if you could describe the 3-dimensional location within the vehicle where you believe you are hearing a knock.

The Mazda CX series of vehicles that are "SkyActive-Drive" and AWD have the most rotational play in the front and rear drive shaft than I have seen to date. I have personally experienced a slight "knock" coming from these drive train components during the break-in period of my new 2018 CX-9 Signature. I specify "during the break-in period" because over time the knock has become less noticeable. However, it is still present and I notice it becomes more pronounced with higher ambient OAT. I've come to the conclusion that at or below 1,200 rpm, either the clutch and/or torque converter are not as well sync'd as they could be. Or, maybe this is as good as Mazda can make it given the new torque converter design they implemented into the CX-9 (not sure of the Mazda 6 shares the same converter).

The CX-9's transmission is supposed to be a hybrid design offering the best qualities found in a conventional automatic and manual or dual clutch transmission to provide on-demand torque with faster on-set and reduced lag. I applaud the effort by Mazda (I really do). However, it is my belief that one of the drawbacks of their attempt comes with a missing level of refinement in the smoothness of the transmission at or below 1,200 rpm in a heavier vehicle - where sometimes the engine output is not sync'd adequately throughout the rest of the drive-train to prevent this "clumsy" kind of transference of power down to the wheels at near idle RPM. I doubt this is an issue with the Mazda 6, because of its lower curb weight.

I think this has to do with the weight of the vehicle combined with the new torque converter design. On a full tank of fuel, this "lugging" (what you call knock) is dampened to the point of almost being imperceptible. When the vehicle is lighter, the low RPM lugging comes back on throttle-up while rolling and from a low RPM condition. I don't think there is anything "broken" here. I just think this is a "design characteristic" of the CX-9's drive-train in particular depending on how your CX-9 made it through its break-in period (you may have more or less lugging/knocking) and was ultimately set-into its mechanical tolerances (every new vehicle will vary slightly/fractionally after set-in).

In short, the vehicle is trying to give you on-demand access to greater torque at a faster rate pf on-set and from a lower RPM. That's the important part to remember - from a lower RPM. That's the primary job of a transmission - to efficiently manage and direct engine output to the wheels (ultimately). At 4,300 pounds howerver, that whole process needs to be as smooth as possible throughout the entire RPM band.

I think the problem is in the Lock-Up of the Torque Converter, quite honestly. Mazda, designed the new torque converter to have an extended lock-up time which extends the time the engine rotation is directly linked to transmission rotation - specifically from lower speeds - which means from lower RPM. They claim lock-up ratio increase of 30% over the previous torque converter design used in their vehicles. When they did this, they also were forced to re-design their Clutch to include multiple discs and a larger vibration damper spring.

I like it. It's just not as "refined" as it could be and that's why we are hearing the "lug"/"knock" at our door - or under the vehicle to be more precise. I'm going to be talking with Mazda soon about my paint. When I do, I'm also going to engage them about the reason behind so much rotational play in the front and rear drive shafts - while all four drive axles have precious little rotational variance. There has to be a engineering reason behind so much play in the drives.
 
I took it to the dealer yesterday and they told it is normal. The technician said that it is a normal noise coming from the relays and other components related to the MRCC. Don't know if BS or not. My previous Mazda 6 2014 with the MRCC feature never made those noises whe accelerating by itself. Can anybody else verify this noise when using the MRCC?

Sounds like BS to me. If you are reporting the same "knock" that I describe in my reply, this has absolutely nothing to do with MRCC components.

Listen, I never take any new vehicle I've ever owned directly to the dealer without first calling the OEM, reporting my problem (making a claim) and then having an OEM representative (usually corporate customer service) make the dealer appointment on my behalf. That way, when I arrive at the dealer the service manager has already been contacted by corporate, read the complaint and tends to deal with the matter more seriously.

I don't drive into a dealership with a "problem." I drive into the dealership with an OEM documented "complaint" and an OEM scheduled appointment. This puts everybody on notice and it starts the documentation off right, if the matter turns into a Lemon Law case. In other words, I notice everyone up front that I'm not interested in wasting my time with being told that the Torque Converter an Multi-Disk Clutch design coupled to a wide rotational variation in the Drive Shaft that's causing "knock" during acceleration from low RPM, or "lugging" between 1,200 RPM and 900 RPM, is somehow being triggered by the Radar Cruise Control System's components. The more specific you can be before you enter the dealer for inspection and the more homework you can do on the probable mechanical causation, the more you can focus their attention and the more BS cycles you can knock down before they actually solve the real underlying problem.

Here's the deal. Dealerships have underlying contracts with OEMs to do warranty work on your vehicle at much lower rates than what they can charge you retail as a customer. Dealerships have a limited number of racks and a limited number of mechanics. Those are both revenue generating assets to them. If their rack and mechanic is being "tied up" with OEM contract work - then then they are not charging you $300 for an oil change and not up-selling you on service and maintenance that you don't need or could easily wait another 40,000 miles to do. If they can chase you away with a BS MRCC or XYZ storyline (knowing full well they are lying to your face) then that allows them to fill that workspace with a vehicle that increases their revenue for the quarter.

Here's where we are in the United States. The police can lie to you in order to get you to incriminate yourself. They can tell you something that is not true, get you to say something you never should have said and then ding you with a citation or arrest for having done so. Perfectly legal. A dealer can lie to you in order to get you to leave their facility, so that they never have to do warranty work on a vehicle at a much lower rate paid by the OEM - while using their limited assets to charge another customer higher rates for doing work that is either out of warranty and/or completely unnecessary. That's the world we've created for ourselves. That's the economy we tolerate.

- Educate yourself as much as possible about the matter before visiting a dealer
- Always file a complaint (if under warranty) with the OEM directly and get them to set your appointment with the service manager
- Get the OEM (corporate) to agree to a final solution that fully satisfies you (this is who you negotiate with - not the dealer)
- Let the OEM (corporate) know how "happy" or "unhappy" you are with your vehicle and why

Leverage the OEM to assist you at the Dealer. Never "Cold Call" a dealer about potential warranty work. They will often give you the cold shoulder, if you do. Warm things up through the OEM, first - then go visit your OEM scheduled appointment at the dealer. Back-up and try again using the above with a different dealer and then notice the different outcome. The Mazda USA phone number is in your "Warranty Information" manual on page 8 (for 2018 models).

Mazda, is a good company. The dealer network is sketchy. You may have to work a bit to locate a solid dealer near you. All the best with this.
 
Well in my case it's a single knock sound just after the break is released by the system when you press Resume or when it accelerates by itself. It does it every time. Something is knocking some metallic area or part.

I tested it yesterday on my way home from work. Climate control off, radio muted, all windows closed. MRCC set to 55 km/hr in stop and go traffic. Every time I resumed from Hold, it was whisper-quiet, no knock sound of any kind. If I was in your position, I wouldn't accept that explanation that the dealer gave you. Can you record a video of the knock sound?

If you'd like, I can record a video of my test on my way home from work today, so you can take it to the dealer and show them the lack of noise on my vehicle and compare it with the noise on yours.



You can also try tightening a few things under the hood as described in this thread: https://www.mazdas247.com/forum/sho...ocking-noise&p=6607411&viewfull=1#post6607411

Probably totally unrelated, but it's free, quick, and you can check it all out on your own time at home. Who knows, one of these fixes (loose strut tower bolts, loose cowl, loose fuse box cover) could be the culprit.
 
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