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soft/low brake pedal

Discussion in 'VR - VS Holden Commodore (1993 - 1997)' started by sxi ss, Sep 2, 2011.

  1. sxi ss

    sxi ss Member

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    hi my vr ss has vt front brakes , vt master cylinder and booster fitted, zinnoli dds rotors and hard pads fitted , i just cant get the pedal right on it, tryed 2 boosters/3 master cyklinders and 2 sets of calipers help please
     
  2. hako

    hako Donating Member

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    Have you bled the system of air completely?...a pressure bleed is best as it really forces the fluid thru the lines.
    Did you use the pushrod from pedal to booster from the VT...not sure if this matters.
    I've usually found that it takes a week or so for the pads to bed in to the shape of the disc, and during this period the pedal will be soft and low. Hard pads will take longer.
     
  3. oscar03

    oscar03 New Member

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    check for air. a problem like that is sometimes an indication that there is air in the rear lines. it causes the pedal to travel further before having much effect and then is very spongy. air in front lines tends to brake for a moment then fall away really quickly and also has a spongy peddal. also air can be hard to find sometimes just because you cracked the bleed nipplle a few times and didnt see any bubbles doesn't mean its free of air. i have used a large syringe and clear rubber hose to suck throuh the brake fluid before this works pretty well you just need to be carefull not to let the master cylinder go dry or you are back to square 1. thats just from the experiance i have had in the past not any specific source. but i hope it helps
     
  4. sxi ss

    sxi ss Member

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    the car has had this issue ever since i have had it about 2 years , pads and rotors done 6 months ago, master cylinder, booster and fluid swaped again yesterday, no better than standard vr booster master cylinder setup, swaped front claipers and rebleed today , still the same,,, clamp front brake hoses and pedal is great so im picking it has to be in the front end somewhere, what are the shims people talk about on here when putting vt brakes onto vr's i dont know what hubs mine has as i didnt do the origional conversion , i just got stuck with the headache
     
  5. BlackVXGTS

    BlackVXGTS Well-Known Member

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    Did you bench bleed the master cylinder before you installed it?
     
  6. sxi ss

    sxi ss Member

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    i have no idea a local garage done it for me , im asumeing they know what they are doing
     
  7. hako

    hako Donating Member

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    Try a brake place - get them to pressure bleed the system.

    Edit....found this on another thread - may be relevant - if bleed nipple is not at top you may not be able to bleed all the air out: "might pay to add that you gotta make sure the bleed nipple is at the top when fitting new calipers."
     
    Last edited: Sep 2, 2011
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  8. RX25SE

    RX25SE Real cars are steel cars.

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    Has the booster pushrod been adjusted correctly?
    If not, it may be preventing the compensating port in the m/cyl from being open when the brakes are released.

    Are you getting plenty of fluid when you bleed it?
     
  9. pete30nz

    pete30nz Member

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    Hi people,
    My vr v6 abs brake pedal was right to the ground before it would start to work last week, the car had been sitting around for over a year.

    We put another brake master on, fresh fluid through system, and bled it half a doesen times, but the pedal still went to the ground with out trying hard to push it.

    Turned out the slides on the rear calipers were seized.

    Replaced front and rear piston seals, re bled system with engine running, and with engine turned off.
    I have a better pedal there now, but would be great if It could be better like a non abs pedal?

    Hope this can help some one with any brake issues.

    Pete
     
  10. pete30nz

    pete30nz Member

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    Update: my Vr was taken for w.o.f recheck, and the brake pedal still failed. The w.o.f man said the pedal should be firm like his late model commodore.
    We swapped over calipers last night and bled the system as good as we could, but pedal still has at least an inch or more travel.

    The front passenger wheel is really hard to turn with brake caliper on, i used a 2 foot bar between wheel studs to turn hub, with lots of strength, and it moved very slow.??

    I haven't tried clamping any brake lines at this stage, I need some clamps that I don't have.

    Must still be air in the lines I'm guessing, because the pedal has at least an inch and more travel in it...?

    Any ideas will be appreciated please

    Pete
     
    Last edited: Dec 13, 2016
  11. Jxfwsf

    Jxfwsf Well-Known Member

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    With the engine off, does the pedal pump up firm?
    Give it a few minutes, is it still firm or does it require you to press it a few times?
    If there are no visible brake fluid leaks, get someone to watch each of the brake hoses 1 at a time (the flexible black hose, 5 in total inc the rear body to diff) while you press the pedal, are any of them shot and expanding like a balloon?
    Is it the firewall flexing 1"?
    Are you using the cheap brake pads?

    How do they test it over there?
    Is it upto date using a calibrated machine that measures the vehicle speed, pressure applied to the pedal and deceleration of the vehicle?

    Oh and you don't bleed brakes with the engine running, it's a simple hydraulic system, not trying to stop 2 tonnes with aid.

    Not the case here, but if it's a 20 year old system, the last thing you want is the piston seals scraping through the buildup of crap in the bore and tearing the seals up. Only use half at most of the pedal travel to pump up and bleed (sit your other foot under the pedal so it can't go to the floor), you've probably seen the crap and buildup in a reservoir, now think about it sitting in the bore and a rubber seal running over it a few times where the piston seal normally doesn't go.
     
    Last edited: Dec 13, 2016
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  12. pete30nz

    pete30nz Member

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    EDIT: my last message mentioned wheel was hard to turn. The caliper i had swapped to try had a sticky slide, which we freed up and wheel was turning fine again.
    Also I clampped front brake lines and with engine running pedal was firm as, clamped rear hoses and with engine running pedal was not as firm.

    Hi Jxfwsf,
    I just checked the thread now.
    Thanks for messaging.

    Yes with engine off the pedal is high and firm as, and doesnt seem to change.
    But start the engine and pedal is about half travel be for you feel any thing and soft.
    With engine running yes it takes 3 or more pedal presses to start feeling better, but still spongy.

    When you say about flexing, mite you mean is the booster moving forward as i pump the pedal? It doesn't move much at all since I refitted the bracket at front of master cylinder.

    When they test the brakes at w.o.f shop they use the roller in ground system over here with a screen.

    I'm using calibre brand brakes pads about $50 - $55

    Next time we bleed the system, I'll get my mate to pump up the pedal but only pumping half way pedal?. Then does he hold down to the floor while i crack the nipple?


    Thanks heaps

    Pete
     
    Last edited: Dec 25, 2016
  13. the_boozer

    the_boozer no more VK

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    the only thing in this thread thats not all ready mentioned on things that can get fucked up with brakes maybe I only think its an issue because it had me fucked once, have you lost the reaction disk in the booster push the brake pedal in the the master cylinder off will do it. If the brakes bleed up nice and hard then go soft / spongy when the engine starts is the give away.
     
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  14. immortality

    immortality No more smoky bacon :( Staff Member

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    If the brake pedal is rock hard with the engine off and then sinks when you start the engine there is a problem with the brake booster as it's loosing vacuum. If you start the engine and allow vacuum to built in the brake booster and then switch the engine off you should need to pump the brake pedal 3 or 4 times to deplete the vacuum in the booster and the pedal will go firm again. If you start the engine and allow vacuum to built in the booster and then switch the engine off the booster should maintain a vacuum. Simple test is to check the brake pedal after a short period, if the pedal drops as per normal then it's holding a vacuum, if the pedal is hard then it's got a vacuum leak. This unfortunately is fairly common on older cars. Most likely the one way valve is stuffed or worst case it is loosing vacuum via the push rod seal in which case the booster will need replacement.

    All brake pedals will have some travel before the brakes actually start to work, this is good because it they came on as soon as you touched the pedal it would be bloody dangerous. the WOF guy is talking crap if he's comparing your 20+ year old Commodore to his new one. probably best to compare you brake pedal to another commodore of the same vintage.

    IMHO cheap brake pads (that really aren't that cheap) from supercheap just aren't worth the effort. I did the front pads on a 2002 Subaru last week with decent pads from BNT and the retail price was roughly the same as the Callibre pads you put in and the bonus was a firmer pedal.

    I use an old medical syringe to suck all the old fluid out of the reservoir and fill with new fluid before doing anything else. If it's real dirty wipe out with a cloth before re-filling.

    If you don't want the pedal to fully depress to the floor find a bit of wood to put under the pedal. put car up on stands and remove all 4 wheels and then start bleeding at the wheel furthest from the reservoir working towards the closest one. Bleed each caliper until clean fluid comes out. Because you are doing a full bleed you will need to regularly top up the reservoir, if it runs empty and gets air into the system you will need to start over again.

    Bleeding is simple, have your assistant pump up the pedal and then apply pressure, you then crack the caliper bleed nipple and allow the old fluid out, as the pedal drops and the flow reduces close the bleed nipple. Make sure your assistant does not release the brake pedal until after you close the bleed nipple or you will draw air back into the caliper and **** it all up again.

    My boys are great assistants, commands are simple. Pressure and release. If your assistant can't follow those 2 simple instructions find another assistant.

    Failing all this take it to a local workshop, (it hurts to type this) but your local Midas just might be the go.....
     
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  15. Jxfwsf

    Jxfwsf Well-Known Member

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    Try different pads, calibre really aren't that great (probably fine for the grand parents in their lil kia ducking down to the shops) and last time I tried a set it was a soft squishy pedal.
    Although surprisingly they did pass a rwc test here a couple of years ago, new set of decent pads and the squishy pedal problem went away.

    Was the same with a set of "repco" pads on a VT, tried flushing and bleeding the system trying to make it feel better with no success, threw in a set of slightly used bendix, magically no more squishy pedal.
     
    Last edited: Dec 27, 2016
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  16. pete30nz

    pete30nz Member

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    Hi the_boozer,
    I've never heard of the reaction disc, which leaves me asking where exactly does it sit.
    I'll have a look and confirm if its there once I know where it sits.

    Immortality and Jxfwsf,

    I had the car in at safe r brakes and Pitstop,
    Pitstop bled the brakes for me, unsure how they actually did it.

    I'll try some new brake pads, other than bendex what are other good brands of pads you know of.
    And I may as well try the half way pump while bleeding brakes to see if it makes a difference for me.

    Thanks fellors for the replies
    Cheers pete
     
    Last edited: Dec 28, 2016
  17. immortality

    immortality No more smoky bacon :( Staff Member

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    For your average daily run around I use and recommend the BNT Cplus in-house brand brake pads. They are a low dust ceramic formulation that work well and are reasonably priced.
     
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  18. Jxfwsf

    Jxfwsf Well-Known Member

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    If it's been bleed there is no need to do it again.
    Just push the pistons back in (it won't be very far if the current pads are new) and won't do any harm just to fit a different set of pads.
     
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  19. Brisbarnz

    Brisbarnz Active Member

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    Does it have abs?
     
  20. the_boozer

    the_boozer no more VK

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