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Thread: New MPS owner: Mazda 6 MPS 2005 Strange Knocking Noise

  1. #1

    Default New MPS owner: Mazda 6 MPS 2005 Strange Knocking Noise

    Hey Guys,

    i bought a mazda 6 MPS 2005 model last week, and have noticed a strange knocking senstation that occurs in the car.

    it happens about 1/3 times as the car is decelerating no matter if in gear or in neutral. usually happens at about 10-20km/h at 2-2.5krpm.

    Feels as if the car has ran over a pot hole but it hasnt? sort of like a jerk/knocking sensation. from inside it sounds like its comming from the rear diff, or around that area.

    the car is stock except that it is lowered on springs.
    i should also mention that it does require a service...

    what you think?

  2. #2
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    Welcome mate and congrats on your purchase. First thing to check is tyre pressures, second is are all 4 tyres the same! Reason being is that with the AWD a difference in the diameters of the tyres particularly rears left/right will cause some drivetrain knocks and noises on deceleration, also front to rear size differences will also produce knocks and vibrations.

    Try that first then have a look through the Tech Talk area which contains a number of diff related threads which may help you. A number of members have lowered MPS 6's without problems so it may not be that.
    R36 - Just like an MPS6 except with a growly V6

  3. #3

    Default

    Thanks mate ! got some big plans for the car, so you'll be hearing alot form me lol

    Now that you mention it, the two front tyres are different to the two rears... but if it was that, wouldnt it cause a reoccuring knock if that were the case? not just a single severe knock?

  4. #4
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    Quote Originally Posted by shakespeare View Post
    Welcome mate and congrats on your purchase. First thing to check is tyre pressures, second is are all 4 tyres the same! Reason being is that with the AWD a difference in the diameters of the tyres particularly rears left/right will cause some drivetrain knocks and noises on deceleration, also front to rear size differences will also produce knocks and vibrations.

    Try that first then have a look through the Tech Talk area which contains a number of diff related threads which may help you. A number of members have lowered MPS 6's without problems so it may not be that.
    rayd, hello and welcome to the forum. Shakespeare got it right in one I reckon. I had a similar prob with my '05 MPS6, vibration on deceleration just as you describe. My local mazda dealer (REGAL MAZDA Newcastle.... I cant say enough good things about them) went to EXTREME lengths to chase down the problem. It turned out to be Yokohamas on the front and Toyos on the back that were causing the problem.

    Although both pairs of tyres were 225/40R18's and ostensibly the same size they must in fact have different rolling diameters or different coefficients of friction. The rear diff (because the car is not constant 4WD) was basically going "I'm slipping, I'm gripping, I'm slipping... " and causing the vibration you mention.

    If you can, try to borrow a set of identical wheels and tyres that fit your car and take it for a drive. I think you will find your problem will be solved.

    Good luck with it,

    Leon
    Started out with nothing Still got most of it left

  5. #5

    Default

    Swopping front to backs would be worth a try, as it costs nothing.

  6. #6
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    Quote Originally Posted by foxy View Post
    Swopping front to backs would be worth a try, as it costs nothing.
    Nope, wont work.

    Leon

  7. #7

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    Ok, ill look into that, but the only thing i want to point out is that it isnt a vibration. it is just one hard knock as if i hit a pot hole. not a constant knocking... thats the only thing that is leading me to think that it isn't the tires...

  8. #8

    Default

    If there is a problem with tyre height, it will be because the car IS constant awd. That is to say, when ever the car is in motion, all four wheel are constantly driven (only the torque distribution varies). If there is a tyre height variance, it will cause the drive line to wind up, because the diff coupling doesn't slip much and doesn't disengage until the car almost stops (around 5kmh). Just to be clear, the 6MPS is not "AWD on demand".

    There are two things you can do to check if it's a tyre height issue.

    1. Apply the hand brake to the first notch and confirm the light shows on the dash. This will turn off the rear diff. Drive around and try to replicate the knocking sound.
    2. If this experiment stops the knocking, measure the tyre height on a flat level surface, from the ground to the top of the rim. Any more than about 4mm variance will cause problems.

    If there is a significant variance, you can play with tyre pressures to try and balance the tyre height. Just be careful because a significant variance in tyre pressures obviously has its own issues and this just for diagnostic purposes.

    Good luck. I hope it is just a tyre issue because it's a whole lot easier to fix than some of the other drive line problems.

    Gone to Volvo


  9. #9

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    Quote Originally Posted by kmh001 View Post
    If there is a problem with tyre height, it will be because the car IS constant awd. That is to say, when ever the car is in motion, all four wheel are constantly driven (only the torque distribution varies). If there is a tyre height variance, it will cause the drive line to wind up, because the diff coupling doesn't slip much and doesn't disengage until the car almost stops (around 5kmh). Just to be clear, the 6MPS is not "AWD on demand".

    There are two things you can do to check if it's a tyre height issue.

    1. Apply the hand brake to the first notch and confirm the light shows on the dash. This will turn off the rear diff. Drive around and try to replicate the knocking sound.
    2. If this experiment stops the knocking, measure the tyre height on a flat level surface, from the ground to the top of the rim. Any more than about 4mm variance will cause problems.

    If there is a significant variance, you can play with tyre pressures to try and balance the tyre height. Just be careful because a significant variance in tyre pressures obviously has its own issues and this just for diagnostic purposes.

    Good luck. I hope it is just a tyre issue because it's a whole lot easier to fix than some of the other drive line problems.
    Wow, thanks for that, ill be sure to try out the hand brake trick tonight when i get home. i really hope that this is the issue aswell!

  10. #10
    Join Date
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    Quote Originally Posted by kmh001 View Post
    If there is a problem with tyre height, it will be because the car IS constant awd. That is to say, when ever the car is in motion, all four wheel are constantly driven (only the torque distribution varies).
    You are absolutely correct, that is a better way of phrasing it. My "car is not constant 4WD" statement was an attempt to get across the idea of the variation of drive to the rear wheels.

    "AWD is in constant operation except at very low speed and when the hand brake is applied" as is stated in this YouTube vid. YouTube - Mazda MPS 6 AWD operation

    Thanks for putting the record straight.

    Leon
    Started out with nothing Still got most of it left

  11. #11

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    No worries. The reason I stressed that point is because one of the first published reviews of the 6MPS contained a few incorrect assumptions made by a lazy motoring journalist who didn’t do his job properly. Amazingly, virtually every other published review contained the same incorrect assumptions and false information about how the AWD system works. I think it shows these guys do little more than plagiarise each other to cobble together bumf that fills the spaces between ads.

    But this means that a lot a new and prospective owners, having done their research, are left with an incorrect understanding of the 6MPS AWD system due to the false information that was propagated by numerous motoring publications.

    Given this is one of my pet subjects, I like to make sure new owners are properly informed. Especially given that the AWD works a lot better in performance terms than they may have been lead to believe.

    Ok, back to topic.

    Gone to Volvo


  12. #12

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    Ook! Bit of an update!

    I did the hand break one click thing and the noise disappeared , so it was the rear diff, I went and put 38psi into all 4 tires and noticed that the rears were at a low 27psi compared to the fronts at 32psi. Drove around for abit and I dont think the knocking is occurring. I'll test again soon

    Hopefully it was from the tyre pressure difference!!!

  13. #13

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    Thanks for the update. Glad it was something simple.

  14. #14
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    Pleased to hear you had a win. Do tho, just as soon as you need to replace your tyres, aim to put 4 identical tyres on the car. MPS6's do not like to have different tyres on the front and rear.

    Leon

  15. Default Hi and thanks for the info

    Firstly, a big hello to you all from Old South Wales (that small but wonderful place unfortuantely attached to England ....just kidding for all the poms on this site!)

    Bought a 2007 MPS 6 last week which was fine but then suddenly started to feel like the diff/gearbox had gone which was causing a jerking banging noise from the car.

    After reading this thread I checked the tyres and they were different makes on the front & rear. Tried the handbrake trick and it worked perfectly....no more knocking.

    Got 4 new Hankook Evo tyres this arvo and car now driving perfectly

    A Garage told me the gearbox was gone......

    Think I'm going to be on this site a lot!!

    Cheers for now.

  16. #16
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    Quote Originally Posted by angrydad View Post
    Firstly, a big hello to you all from Old South Wales (that small but wonderful place unfortuantely attached to England ....just kidding for all the poms on this site!)

    Bought a 2007 MPS 6 last week which was fine but then suddenly started to feel like the diff/gearbox had gone which was causing a jerking banging noise from the car.

    After reading this thread I checked the tyres and they were different makes on the front & rear. Tried the handbrake trick and it worked perfectly....no more knocking.

    Got 4 new Hankook Evo tyres this arvo and car now driving perfectly

    A Garage told me the gearbox was gone......

    Think I'm going to be on this site a lot!!

    Cheers for now.
    Glad you found an answer
    It's always nice when something comes out much cheaper than originally expected!
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  17. #17

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    My 07 Mps 6 is making a wicked thumping noise which i notice more of down shift it's annoying, the dealership has told me they recon it's a internal problem in the gearbox and are pulling the box out to look, has anyone else experienced this sort of problem?

  18. #18

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    could be one of your mounts?

  19. #19

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    I asked that question and they said all the mounts are fine, Kinda disturbing that fact the car only has 64,000 on it but i guess no matter what car you buy, they all have problems so worse than other.

  20. #20
    Join Date
    Aug 2010
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    Quote Originally Posted by Supereunos View Post
    My 07 Mps 6 is making a wicked thumping noise which i notice more of down shift it's annoying, the dealership has told me they recon it's a internal problem in the gearbox and are pulling the box out to look, has anyone else experienced this sort of problem?
    Can you tell if it's coming from the front or rear of the car?
    I'd be double checking the diff mount bolts, and it never hurts to check the wheel nuts too.

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