Section : Rear Axle

Rear axle, brakes, wheels and tyres.

Soft brake pedal

Posted By : Stephen McCrory, 27-May-2003, 08:48pm

Hi
Since I replaced the calipers on my spitfire I have had a soft pedal. I bled the system in the usual way and then using an easibleed - still no joy. Any tips? Is the master cylinder shot? If so how can I tell? Are repair kits any good? HELP!
Thanks
Stephen

Followups :

Soft brake pedal

Posted By : Daniel James, 28-May-2003, 11:05am

next time you are in the car, pump the brake pedal, and see if it 'stiffens up' if it does, you have air in the system, and it need's bleeding. You need to bleed the whole system, not just the part you replced the calliper on. (assuming you have single circuit brakes?)

In my (limited) experience repair kits are not worth it, unless you know that the piston etc are in good condition you are much better off getting a whole new master cylinder.
- Soft brake pedal
  
  Posted By : Michael Davis, 28-May-2003, 01:04pm
  
  The brake pedal will also stiffen up when pumped if the rear shoes are in need of some adjustment.
  
  Actually this is free play being taken up rather than actual stiffening after the pedal begins to "bite" as it squeezes the fluid so should feel different but I just thought I'd mention it.
  
  Mik
  - Soft brake pedal
    
    Posted By : Stephen McCrory, 28-May-2003, 09:48pm
    
    Thankyou,
    Thats confirmed that the master cylinders okay, and its air in the pipes. Any tricks to actually get it out?
    I appreciate your patience!
    STEPHEN
    - Soft brake pedal
      
      Posted By : Gordon Davies, 28-May-2003, 10:41pm
      
      After years and years of adjusting rear brakes the conventional way, I took a tip from a web link to a US site - can't remember which one though. Jack rear wheels up one at a time. Pull handbrake up 3 notches.Adjust each side until wheel "binds" but still turns by hand. Easy. Handbrake is adjusted correctly at the same time.
      And I can now stop in less than a mile from 70mph !!!
      
      Gordon Davies
      - Soft brake pedal
        
        Posted By : Daniel James, 29-May-2003, 08:41am
        
        You will need someone to press the brake pedal (while outside of the car).
        
        You start at the wheel furthest away from the master cylinder, loosen the bleed nipple right off, put the eezibleed on (anything you can do to make the union more air tight, eg holding it on! is better), then get someone to push down the brake pedal, then tighten the nipple (I know the ezibleed says it has a non return valve, but I don't trust them!) then release the pedal, then loosen the nipple, push the pedal....carry on until 3 pumps of the pedal after you stop seeing air bubbles in the fluid. then check the level of the fluid, then repeat the excercise on the other wheels. The Haynes manual has a good description/pictures etc
        
        Incidently... I'm sure you know, but you have to be very careful about handling brake fluid, if you knock it about you'll get air bubbles in it, and it takes a long time to 'settle' also it's a very effective paint stripper.
        
        Soft brake pedal
        
        Posted By : Nigel Gibbins, 29-May-2003, 12:14pm
        
        I have a slight clarification to Daniels message (sorry Daniel) please pardon me. :P
        
        When bleeding the brakes you should start with the one furthest from the master cylinder by the route the brake pipes take e.g. the one with the greatest pipe length. The Master feeds into the union and then on to the slave cylinders so you can work it froim the union instead. The union is usually located next to the rear lower wishbone mounting point on the nearside chassis rail. (Passenger side for UK cars)
        
        This usually makes the order OSR, NSR, OSF, NSF.
        
        NiG
        http://www.niginthecar.net
        
        Soft brake pedal
        
        Posted By : Adrian Lee, 30-May-2003, 08:20am
        
        In addition to Nigel's sound advice, use Castrol response fluid, it's a bit dearer but does not have the nitromors quality of conventional brake fluid and does seem to work better.
        
        Soft brake pedal
        
        Posted By : Daniel James, 30-May-2003, 08:26am
        
        You may as well swap the brake fluid while your at it... make sure you use the correct 'dot' rating, if you use the wrong one the seals won't cope (or something... sorry... a bit vague) and I've heard silicone fluid compresses more then 'conventional' fluid, so won't give quite as good feel...
        
        Soft brake pedal
        
        Posted By : Daniel James, 30-May-2003, 08:27am
        
        oops... I've been doing it wrong then... oh well...