big_wasa
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| posted on 22/1/12 at 11:25 AM |
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Brake problem, what am I missing ?
Set up.
Twin master cylinders on a bias bar pedal box.
M16 front calipers.
Braided hosses upto short solid pipes on a bracket as per cortina.
All worked fine untill I changed the front solid pipes from copper to kunifer.
Ive now got pressure in the front system with the front wheels very stiff and the brake light on.
Its doing this with no pressure on the pedal.
The biass bar is free to move and the push rod to the cylinder has a tiny bit of play so is not pre loaded
The pedal is hard and not spongy and does not sink with pressure.
If I open either of the front bleed nipples it lets a small amount of fluid out and lets the pressure of. The wheels spin and the brake light goes
out. Untill you press the pedal again.
Ive let it stand since last week and it had still held the pressure in the line.
Any ideas please ?
I am a bit stumped.
As I say the only change has been the front solid pipes and some firm pedal pressure to test for leaks......
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woolly
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| posted on 22/1/12 at 11:36 AM |
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sounds like the small valve seal on the end of the piston spring has swollen or the piston is not returning completely
if when you dismantle it all the seals feel very soft check you have used the right fluid.
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JeffHs
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| posted on 22/1/12 at 11:37 AM |
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My money is on the master cylinder push rod having too little play. I had this problem on my car but it didn't appear until everything got hot
on the first drive to SVA. Perhaps the problem has always been there but you've done a better job of bleeding with the pipe change?
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mark chandler
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| posted on 22/1/12 at 11:58 AM |
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Does sound like the master cylinder plunger not returning far enough to release the pressure, if so you will need to shortern the pushrod by a couple
of mm which will then allow the seal to uncover the hole.
Can you pull the boot off and have a look in the bore, see if the plunger is 1/4 way down when the pedal is all the way up? If so this is your
problem.
If the rod is loose then something is sticking, if both sides are stiff to turn then its the master cylinder.
Regards Mark
[Edited on 22/1/12 by mark chandler]
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jossey
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| posted on 22/1/12 at 01:28 PM |
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piston me thinks.
Thanks
David Johnson
Building my tiger avon slowly but surely.
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big_wasa
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| posted on 22/1/12 at 04:15 PM |
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Well ive been buggering about with it all afternoon.
There is no pre load on the cylinder. And it was fine before.
Looks like I have over pressured the the master and the switch.
The brake switch is had it. Having bypassed this and re-bled the system its alot better.
More bits to buy 
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