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We are building a bush hack out of bits lying around and we have a brake problem - using a FB/EK brake master cylinder and a Gemini front end with disc brakes , all bled up nicely but the brakes don't clamp with any force - if we block the hoses we have a firm pedal but once it's all together the calipers move but don't grab properly and the pedal is virtually non existent??? Maybe more bleeding or will this never work because the master doesn't have enough volume ???

Should work, when you say pedal non existent do you mean soft or going to the floor ?

Sounds like could still be air in there somewhere.

Regards Greg

Be sure the calipers are mounted so that bleed screws are higher most. I’ve been caught in the past when calipers were swapped to opposite sides and therefore turned upside down.


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calipers are the right way around , havent checked pushrod clearance yet , might not be getting enough travel , will try that when I get home on Wednesday. I have been told by a brake guy that it SHOULD work so just need to figure out why it isnt ........

Try bleeding it in reverse.. use a big siringe and blow the fluid from the caliper back up to the master cylinder.... or sometimes if you just compress the pistons right back into the calipers it will blow the stuck air lock back into the master cylinder..

But I think you will find that the master cylinder size is actually to big and in affect is not making enough pressure to give the calipers enough clamping power, try pushing hard on the pedal and I bet that the rear drums ( presuming that it still has rear drums) are clamped up tight while the discs are doing nearly nothing..

no rear brakes - set up for donuts in the dirt

How about trying a clutch master cylinder instead? They should have a much smaller cylinder in then and increase the presure.. and should bolt straight on...

Have you pulled the residual check valve out of the master cylinder? These aren't used when these cylinders are used on discs such as in HR's.
Is the pedal going to the floor or firm?

I think the check valve will only stop the calipers from disengaging, and early clutch master is essentially brake with check valve removed, so doubtful solution I’m afraid.

Are your hoses good?


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Sorry just re-read. Problem must surely be air in the calipers.


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When you say there is no pedal are you meaning it is right at the top and hard as a rock or hits the floor?

Errol62 wrote: Wed Jul 04, 2018 1:06 pm I think the check valve will only stop the calipers from disengaging, and early clutch master is essentially brake with check valve removed, so doubtful solution I’m afraid.

Are your hoses good?


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Yes I am aware of what the check valve is for. I have seen them give trouble when it comes to bleeding systems if they are faulty and as they aren't required in disc set ups I asked if it had been removed.

Craig Allardyce wrote:

Errol62 wrote: Wed Jul 04, 2018 1:06 pm I think the check valve will only stop the calipers from disengaging, and early clutch master is essentially brake with check valve removed, so doubtful solution I’m afraid.

Are your hoses good?


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Yes I am aware of what the check valve is for. I have seen them give trouble when it comes to bleeding systems if they are faulty and as they aren't required in disc set ups I asked if it had been removed.

Sorry Craig
Of course you would be well aware but wanted to make sure that others are likewise.
Cheers
Clay


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We have brakes - the pushrod was about 10mm short , adjusted and the pedal is now nice and firm , but I haven't removed any check valve , where does it live ? I have removed them out of HQ-Z masters but not an early ?