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Brake problem 66 Midget

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scott421

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My Mk2 Midget has developed a brake problem . The fronts seemed to stick on yesterday for some reason .The master cylinder is the tandem type with both brake & clutch master together. This has been stripped and re sealed . There are new copper pipes throughout and areoquip flex pipes . One calliper is new , the other was good and reused when the brake work was done earlier this year.
It was as if they progressively came on of thier own accord . I had to remove the pads and drive the pistons back into the calliper and replace the pads at the roadside to enable me to get home . I limped the car home with precious little use of the footbrake . Been out to the garage tonight and even after standing on the pedal they go on and release as they should.
Stripped the M/C cap and the vent hole is clear.
I didnt have time to take the car out this evening so dont know if the fault will return . Gut feeling is that it will .
Any advice is welcome.
 
I had mine do something similar. I was advised that it might have been a bit of debris causing a one way valve action. So bled through a quart a fluid and the problem has not returned.
 
Also you may want to check the amount of free-play between the master cylinder piston and the rod that attaches to the peddle- there needs to be a little bit of wiggle when the peddle is returned or the piston can block the return flow of the fluid. I had this happen a few times, usually after a rebuild and on hot days, the system would work for several days then on a hot day would lock-up as you say- loosening the rod cured it each time.
Bill
 
Flex hoses. They can be degraded by the fluid and decompose from the inside, blocking fluid from being allowed to flow BACK. Like a one-way valve. That'd be my first suspect(s).
 
Thanks guys, The flex hoses were renewed with the stainless aeroquip style so should be ok (shouldnt fail in 6 months?)
Re the piston/ pushrod , how much play should be there ? its not clear in the manual . Didnt get out this evening so havnt managed to rebleed the system yet.
Thanks again
 
Just enough that you can wiggle it, maybe .010 to .030 inches? just loosen the pushrod until you are sure that it isn't holding the piston in.
Bill
 
Think you are correct, is supose to be about .030 as I remember.
 
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