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Thread: RMM Knock?

  1. #1

    Default RMM Knock?

    I've got a knock coming from the engine bay, usually when accelerating and taking off. Is this a broken OEM rear motor mount? Maybe another mount? Whats the usual telltale signs of a failed mount and how do I check it?

    Thanks in advance

  2. #2
    Join Date
    Apr 2010
    Location
    Canberra
    Posts
    9,459

    Default

    Check by looking under the car...

  3. #3

    Default

    I don't have a jack low enough to jack it up to look. Is there another way of checking without physically looking at it? Just want to be sure before ordering the part.

  4. Default

    Quote Originally Posted by Skeet View Post
    I don't have a jack low enough to jack it up to look. Is there another way of checking without physically looking at it? Just want to be sure before ordering the part.
    Scissor jack that came with the car (along with jack stands)? or create wooden stepped ramps so you will have enough room to get a jack underneath, along with jack stands. The only way is to physically inspect it, no other way.

  5. #5

    Default

    If your drivers side mount was bad you would have oil everywhere and I don't think the transmission one fails much. Thus its probably the rmm, and even if it's not, you want an upgraded one anyway.

    As allo said, jack the car up enough to get your bigger jack under, then lift. If you have a floor jack, there is a lift point under the engine, right where the rmm bolts in and then just use stands. It's easier than it sounds.

  6. #6

    Default

    Awesome thanks for your help guys. Very helpful! I'll try get under it today and take some photos - See what you all think.

  7. #7

    Default

    Okay so I've attached some images of the mount, it doesn't seem to be split or cracked or anything though. Any ideas what else could be causing the knock? It seems to do it on acceleration and sometimes when its bumpy??






  8. #8

    Default

    Maybe it's just dirt/oil, but pic 2 looks like damage to the big rubber bushing?
    You probably have to take it out to really inspect it properly though, or at least undo the centre bolt and let it swing down.

  9. #9

    Default

    I think thats a bit of oil/grease from my hand, I was trying to feel if there was a crack in it. Yeah you're probably right - I was a bit short on time today so I'll jack it up again later today and try get the mount unhooked for a proper look. I was quoted $199 for a Corksport RMM Kit from Fortyone here in NZ so I may end up just upgrading it for future proofing anyway. I can't think what else the knock could be..

  10. #10

    Default

    I've been doing a bit of forum searching and many people have complained about a similar noise coming from the drivers side mount - is that drivers side left hand drive or right hand drive? Is it the oil filled one drivers side on right hand drive or the one under the battery tray?

  11. Default

    oil filled one is the driver's side one (or the passenger side in the US). The other mount is the "transmission" motor mount.

  12. #12

    Default

    Right I had a look at that one and it seems okay from what I can tell. It seems to have a squishy bladder type rubber thing on that bottom that feels quite soft - is it usually soft?

  13. #13

    Default

    Yep. It's literally a bladder filled with manky orange oil. You will know if it has a problem.

  14. #14

    Default

    The sound almost sounds as if its coming from that side of the engine bay. Its almost more of a creak or a crack than a knock on closer inspection.

  15. #15

    Default

    Is it possible the drivers side oil filled mount is buggered even though its not leaking fluid? I'm running out of ideas here lol

  16. Default

    Quote Originally Posted by Skeet View Post
    Is it possible the drivers side oil filled mount is buggered even though its not leaking fluid? I'm running out of ideas here lol
    Its possible. If all the oil was drained then the previous owner cleaned it up you wouldn't even know, unlikely though. Another possibility is that the the bolts on the rear mount are not torqued to spec. Or even your rear diff mount.
    Cheers,
    Brandon Johnson
    CorkSport Mazda Performance
    (360)260-2675 ext. 106
    BrandonJ@corksport.com


    CorkSport.Com

  17. #17

    Default

    True, I hadn't thought of that. I don't own a torque wrench so I can't test to see if its tight enough.

  18. #18
    Join Date
    May 2009
    Location
    Bathurst
    Age
    42
    Posts
    1,930

    Default

    Other possibility, common on 6's. Control arm bushes.

  19. #19

    Default

    Hmm I dont think so - The sound is coming from the engine bay I think.

  20. #20

    Default

    Have you checked that nothing is touching the firewall? I had my turbo replaced and a heat shield was put on wrong so that it clunked and creaked on acceleration.

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