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Griding / poor brake performance after brake caliper change

Discussion in 'Car Repairs / Maintenance' started by johnhull81, 27 May 2010.

  1. johnhull81

    johnhull81

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    Location:
    Lancashire
    Country:
    United Kingdom
    Make Mazda
    Model 323f 1.8i Executive
    Engine size/Type 1840
    Year 1997
    Mileage 146000

    My nearside front brake caliper piston was knacked and causing the brakes to bind on the disc, which has been the case for a couple of weeks (had to wait until pay day to sort it). The pads were also knew as of about a month ago, so I'm not sure if they'd bed in properly before it started to go (I'd done a quick fix on the caliper when I changed the pads).

    I've just changed the calliper and the edge of the disk (the top if looking down on it) is rubbing on the caliper. There's a lot of rust there on the edge of the disc so I'm not sure if that's relevant. My mate said he thinks t hey're 'warped', but my stepdad said it could be a build up of rust that should be 'knocked off' - anyone had any experience of this?

    Further problem is that when I brake the brakes are really ineffective and the pedal goes pretty much down to the floor. I think this suggests I've not bled it properly, but a further problem is that its grinding against the disk and juddering when I brake. The car does stop but it doesn't sound very healthy at all and sounds like its metal on metal (although the pad's thickness seems more than ok).

    I've just read a few articles and it said this might be caused by deposits on the disc from the brakes getting too hot, while the juddering may be caused by the brake fluid boiling. Does this sound like an accurate diagnosis, and if so what course of action should I take?
     
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  3. Peter.N.

    Peter.N.

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    I don't quite understand about the disc rubbing on the caliper, do you mean the outside edge as if the disc were to large in diameter? The pads come between the caliper and disc so cant see how they can be touching that way.

    Having changed the caliper you could well have air in the system and it needs bleeding but if the pads are not being pushed square to the disc that can give the same effect. Bleed you brakes again, making sure you keep the master cylinder full and pump plenty of fluid through.
     
  4. johnhull81

    johnhull81

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    Yes its as if the diameter of the disc is too great (there was some wear on the old caliper where this had been occuring).
     
  5. Peter.N.

    Peter.N.

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    That's very strange, how about the one on the other side, does that have the same problem, if not how much clearance is there between the disc and caliper?
     
  6. Belle427

    Belle427

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    if the caliper was binding you may have warped the disc and also boiled the fluid
     
  7. johnhull81

    johnhull81

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    Sorted it in the end. No idea why it was doing it, but I put new discs on and it was still doing it. The new caliper (from scrapyard but looked fine) was exactly the same as the old one, yet it seemed to sit to close to the disc, causing it to grind on the edge.

    In the end we jacked it up, put it in gear and ground off a couple of mm using a crowbar. There was still some griding with heavy breaking, but that subsided after 20 miles or so.

    Another problem is that there seems to be a lot of give in the steering wheel. This isn't related to the brakes, but wondered if anyone knows what this might be? I've checked to see if the ball joint/track rod end are not screwed in too tight and neither sides are overly stiff.
     
  8. charles5001

    charles5001

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    Your steering rack may be worn.

    I've had this previously, and replaced the old one for a reconditioned one in a "swap em over" deal with the suppliers.

    Worked a treat!
     
  9. Mickymoody

    Mickymoody

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    Still sounds like warped disks, or faulty wheel bearing. I don't follow your last post OP, you 'ground off a couple of mm with a crowbar?'

    Sounds like an accident in the making?

    NEVER get brake components from a scrappy - it might be a scrapper, because that component failed.

    NEVER skim a brake disk with a crowbar (did you do that really?) = faulty brake disk.

    Wheel bearing or steering rack may be faulty, frankly I'm surprised that you are still alive.
     
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  11. Agile

    Agile

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    It sounds as if the disc is worn and has a pronounced lip around the outside.

    There are limits on the depth of the lip which should be used to fail an MOT.

    I solve this problem using an angle grinder. Its a bit risky so I dont encourage anyone else to do it. But I give it for information.

    I jack up the front and remove the wheel. Then after choccing the wheels I put the car in second gear so the wheel disc is turning and then use the angle grinder to remove the lip on each side of the disc.

    This has two advantages, first it enables the brakes to operate correctly and secondly it reduces the chance of an MOT fail.

    Tony
     
  12. Burnerman

    Burnerman

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    Its perfectly ok to remove the rusty wear lip from the outer edges of the disc - usually tapping around with a hammer has this effect.
    However, if the disc is contacting the caliper or caliper bracket then something is way off.
    Either the disc is the incorrect one, the caliper likewise or the hub is bent if the catching is only at one specific point...a worn wheel bearing would produce the same noise.
    If the parts concerned are correct and undamaged, this simply doesn't happen.
    John :)
     
  13. Agile

    Agile

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    Whilst it does not do any harm to remove it as I suggested, its not "correct".

    The manufacturer lays down a minimum disc THICKNESS and removing the lip does not mitigate the minimum thickness dimension.

    Of course the mimimum thickness probably has more to do with selling more car parts than inherrent safety!

    I have encountered grinding when the rust on the lip has expanded to the point it contacts the caliper. It usually wears away after a while but it should be given attention before then.

    Tony
     
  14. Burnerman

    Burnerman

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    No problem with any of that, Tony.
    The minimum thickness is only really vital when the discs are ventilated and there could be a chance of breaking through.
    On many rear disc systems, the wear lip has to be got rid of before you can extract the pads, as the caliper piston has to be screwed in, rather than pushed.
    Any other rust expansion just gets rubbed away as you drive.
    John :)
     
  15. andyandy2

    andyandy2

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    Sounds like a wheel bearing problem to me, would also explain the spongy brakes
     
  16. Agile

    Agile

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    The OP has changed the calipers for some from the junk yard.

    That interupts the fluid and requires the system to be properly blen in accordance with established practice ( to be effective ).

    I would ask exactly how did he bleed the brakes after changing the calipers?

    Even the slightest amount of air creates a lot of spongy movement.

    Tony
     
  17. Mickymoody

    Mickymoody

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    Foolishly in school, when the teacher went away, I stuck a hammer in a grinder, to show my chums the lovely sparks, but teacher caught me being naughty, and explained that high tensile steel, and hardened steel, under those conditions can explode. I had two weeks in the naughty room, and was relegated from metal work, to home economics with the girls.

    The only way I'd skim a disk is via a lathe. But I can now also make a good latte. :LOL:
     
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