Gridgway Posted April 20, 2003 Share Posted April 20, 2003 I have had a search of the archives for this problem, but apart from bleeding and bleeding, I cannot find any other ideas on what to try. On big fronts and standard rears, regular MC, the pedal has been soft since I bought the car, but always works. The pads needed changing which I have done and bled the brakes in the hope that I would make an improvement. All seems the same. Soft pedal with lots of travel, but the brakes do work, they are just not very inspiring. How do I diagnose the source of the problem? How do you isolate calipers without clamping brake lines? Graham Link to comment Share on other sites More sharing options...
StewartG Posted April 20, 2003 Share Posted April 20, 2003 Sounds like you need a big bore master cylinder. Link to comment Share on other sites More sharing options...
Gridgway Posted April 20, 2003 Author Share Posted April 20, 2003 that's possible, but my current setup is identical to the one on my R500 which had a much better pedal. Why should they be different? Graham Link to comment Share on other sites More sharing options...
Miraz Posted April 20, 2003 Share Posted April 20, 2003 I thought your R500 had the AP master cylinder fitted? Link to comment Share on other sites More sharing options...
Gridgway Posted April 20, 2003 Author Share Posted April 20, 2003 nope, standard! Graham Link to comment Share on other sites More sharing options...
mav Posted April 20, 2003 Share Posted April 20, 2003 Have you tried new fluid? How long has the current fluid been in and have you had it tested? Link to comment Share on other sites More sharing options...
Fred Posted April 20, 2003 Share Posted April 20, 2003 i think youl find if you pull the hand brake on your pedal will be good. you could try this, slacken the hand brake cable right off. then screw the pistons right back and bleed once more then adjust the pistons then the cable. Link to comment Share on other sites More sharing options...
Gridgway Posted April 21, 2003 Author Share Posted April 21, 2003 I have adjusted and used the handbrake now the the pedal isn't as long as it was. However, I am still not that happy with it. I think it must be some air. I am also going to bed the pads in some more and then maybe try bleeding again. Graham Link to comment Share on other sites More sharing options...
Marc Newson Posted April 23, 2003 Share Posted April 23, 2003 I have had a similar problem in the past. I even replaced the MC, AP piston seals, pads and fluid. Turned out that it was air in the system, trapped in the rear. Solution: buy a 3 metre length of clear hose that will fit over the bleed nipple. Starting at any corner, connect one end of the hose to the nipple and run the other end into the MC reservoir (secure this end in place as it has a habit of moving). Slowly pump the pedal (and fill MC reservoir as you go - most important!) until you have a continuous circuit of blake fluid. You will see bubbles slowly work their way along the clear tube and you can adjust the speed of your pedal stroke to get the fastest transfer of air along the pipe. Do this for 5 minutes or until you are happy that the circuit is free of air. Tighten nipple and then clamp the end of the hose at the nipple and move to the next wheel. Repeat for all corners. At the end you will have an excess of brake fluid in the 3 m length of hose that you have to carefully dispose of. Marc CUM B48 Link to comment Share on other sites More sharing options...
Peter Carmichael Posted April 24, 2003 Share Posted April 24, 2003 I would only recommend recycling fluid if the system had already been purged with new fluid throughout and even then it encourages moisture absorption. You can achieve air-free brakes without resorting to reuse of fluid. Link to comment Share on other sites More sharing options...
Bare Posted April 24, 2003 Share Posted April 24, 2003 Using a cheap disposable Plastic Syringe with a clear tubing hookup to the Brake Bleeder.. SUCK the fluid /air out of each whhel cylinder. Works perfectly... IF you have problems after this .. yer Master Cylinder should be put directly into the trash bin. Link to comment Share on other sites More sharing options...
JAG Posted April 24, 2003 Share Posted April 24, 2003 The standard rear calipers trap large amounts of air and can be extremely slow and difficult to bleed. Best method involves detaching each caliper from the car (but leaving the brake pipe attached). Ensure the caliper is positioned with the bleed screw uppermost. Fully wind in each caliper piston, then pump them both back out with the pedal. Then bleed each caliper. Repeat this cycle at least four times whilst shaking and tapping the caliper (this helps to dislodge air trapped in the mechanism inside the piston). If you can repeat more than four times then that will help Justin Link to comment Share on other sites More sharing options...
Tony C Posted April 24, 2003 Share Posted April 24, 2003 I used a "Mityvac", it draws a lower pressure at the bleed nipple with a 'vacuum' pump. The hose is long enough that I could bleed my new build brakes on my own. The pump has a small container attached and when that is full of fluid it's time to top up the reservoir. It's possible to pump and observe the master cylinder - just in case. I went round four times and got a good pedal. I could even reach in and exercise the hanbrake while pumping the back brakes. Cheers, Tony BRG SV 😬 Boxes empty, car full Link to comment Share on other sites More sharing options...
Super_Rich_Bernie Posted April 24, 2003 Share Posted April 24, 2003 I watched the mechanics in the Williams F1 pit bleed the F1 car brakes after GP practice. They used a Mityvac - thinking of buying one but they aren't exactly cheap. Much better than the Eezibleed system which uses pressure from a tyre. Jonathan Link to comment Share on other sites More sharing options...
Tony C Posted April 24, 2003 Share Posted April 24, 2003 Mine was £49.36 inclusive. Money well spent IMHO. Link to comment Share on other sites More sharing options...
Marc Newson Posted April 27, 2003 Share Posted April 27, 2003 I too have used a 'mityvac' for that last few years. Still doesn't beat the closed circuit method on each wheel IMO. CUM B48 Link to comment Share on other sites More sharing options...
Barry Bridgman Posted April 28, 2003 Share Posted April 28, 2003 Hi All I always have problem bleeding my brakes it seems to take ages to get all the air out especialy the rears. I have Gunson easybleed that helps. I was thinking of buying a vac bleeder, I was going to buy one that attatches to my compressor. What do people think about this type, would I be better off with a hand pump like a MityVac. Cheers Bazzer Link to comment Share on other sites More sharing options...
Mole Posted April 28, 2003 Share Posted April 28, 2003 I know it sounds obvious but check that you don't have any very small leaks in the system. When I first built mine I had brakes that worked but were "uninspiring". At first I thought this was because the pads needed bedding in, but I traced it to a very minor leak at the joint where the line passes through the bodywork to the front offside caliper. It was so minor that there was no obvious leak, just some seepage of fluid. Once the joint was tightened, the pedal became firm. SV 52 CAT - the mole is awake Link to comment Share on other sites More sharing options...
Barry Bridgman Posted April 28, 2003 Share Posted April 28, 2003 Hi Mole No leaks done loads of track days in it now fluid loss. once done it is fine. It just takes ages to get all the air out. Bazzer Link to comment Share on other sites More sharing options...
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