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nik dando

Disc brake binding/not releasing

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Hi Guys,

 

Just re-rubbered all brake system and changed to silicone fluid, problem is that the N/S disc brake is not releasing after application of pedal, O/S disc brake working correctly, now whats that all about???

 

Had the same problem on daughter#3's Herald a few years ago but I've forgotten how I rectified it although I believe I changed the master cylinder and re-bled, just wondering whether there was an airlock in the system rather than a fault with the M/C and if an airlock is causing the fault on the TR as it is affecting only the one brake, may try that tomorrow. Anyway it is nice chatting these things over, if anyone has any observations or comments I await your reply.

 

The full spec of my system is: Twin bore master cylinder, TR4 (16P) discs and callipers, 10" rear Girling. Was all working fine prior to a wheel cylinder exploding and spraying fluid everywhere which prompted me to repair/replace brake system.

 

Stay happy

 

Nik

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Hi Nik,

 

You should check the flexible hose.

 

It happens once on one of my Spitfire, that I gave to a friend for a rally in Wales, and a brake hose didn't let the fluid go back.

 

Or, it may be a piston problem.

 

Chris.

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Hi Guys,

 

Just re-rubbered all brake system and changed to silicone fluid, problem is that the N/S disc brake is not releasing after application of pedal, O/S disc brake working correctly, now whats that all about???

 

Had the same problem on daughter#3's Herald a few years ago but I've forgotten how I rectified it although I believe I changed the master cylinder and re-bled, just wondering whether there was an airlock in the system rather than a fault with the M/C and if an airlock is causing the fault on the TR as it is affecting only the one brake, may try that tomorrow. Anyway it is nice chatting these things over, if anyone has any observations or comments I await your reply.

 

The full spec of my system is: Twin bore master cylinder, TR4 (16P) discs and callipers, 10" rear Girling. Was all working fine prior to a wheel cylinder exploding and spraying fluid everywhere which prompted me to repair/replace brake system.

 

Stay happy

 

Nik

Hi Nik - Had the same trouble with my Tr3A - it seems to be quite a common fault. All I had to do was adjust the push rod in the pedal box in the engine compartment back 1/4 to 1/2 a turn and it freed the brakes. Hope this is of some help.

BRIAN H. - MEM. NO. 18544

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It could indeed be a flexible hose. But unless you have stripped the entire brake sytem , washed all the lines and cylinders out and replaced all the flexible hoses as well before changing to silicon you will get problems like this. With vigourous bleeding of silicon it ends up with lots of bubbles that are in suspension and take ages to disperse and any old brake fluid remaining in the system wont help either.

Stuart

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Hi Nik,

 

unlikely to be a master problem, if it's only affecting one front.

 

Flexihose is a likely suspect, otherwise it's just another SBF hangup. Lack of lubricant effect on the piston seals, dissolved air in the pipe, or contamination from previous glycol fluid.

 

You could always try flushing the damn stuff out with meths, pdq, and revert to glycol ? Less aggro in the long run.

 

Cheers,

 

Alec

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Thanks for the suggestions.

 

I have stainless pistons in calipers, all seals are new, new rear brake cylinders, some of those nice shiny flexible hoses on the callipers and I flushed the system through before adding silicone brake fluid which had been standing undisturbed on the bench for a month to allow air to escape, then it was poured Oh so carefully and bled non-aggresively. Strange thimg is that the discs free themselves after being left for an hour or two.

 

Anyway I am having a weekend off ('cos I'm fed up) and unfortunately won't be joining in the Drive It Day as was planned. Will let you all know what the outcome is.

 

Nik

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Hi Guys,

 

Just re-rubbered all brake system and changed to silicone fluid, problem is that the N/S disc brake is not releasing after application of pedal, O/S disc brake working correctly, now whats that all about???

 

Had the same problem on daughter#3's Herald a few years ago but I've forgotten how I rectified it although I believe I changed the master cylinder and re-bled, just wondering whether there was an airlock in the system rather than a fault with the M/C and if an airlock is causing the fault on the TR as it is affecting only the one brake, may try that tomorrow. Anyway it is nice chatting these things over, if anyone has any observations or comments I await your reply.

 

The full spec of my system is: Twin bore master cylinder, TR4 (16P) discs and callipers, 10" rear Girling. Was all working fine prior to a wheel cylinder exploding and spraying fluid everywhere which prompted me to repair/replace brake system.

 

Stay happy

 

Nik

 

Nik Does your braking system have the original restrictor valve. This may have gone wrong.

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Nik Does your braking system have the original restrictor valve.

This may have gone wrong.

 

And check another (very recent) thread on the history and

problems associated with this valve - and why you can

dispense with it.

 

AlanR

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Thanks for the suggestions.

 

I have stainless pistons in calipers, all seals are new, new rear brake cylinders, some of those nice shiny flexible hoses on the callipers and I flushed the system through before adding silicone brake fluid which had been standing undisturbed on the bench for a month to allow air to escape, then it was poured Oh so carefully and bled non-aggresively. Strange thimg is that the discs free themselves after being left for an hour or two.

 

Anyway I am having a weekend off ('cos I'm fed up) and unfortunately won't be joining in the Drive It Day as was planned. Will let you all know what the outcome is.

 

Nik

The fact of them freeing off after a while is a classic symptom of Silicon fluid problems associated with incompatable seals swelling up or pipe linings collapsing.

Stuart

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