Pressure in brake fluid

OK so this is the story
1100 Pan 2000 - ABS/TCS/CBS - new seals on front caliper pistons and front master cylinder, new fluid through both front and back. Wheels spin freely before go out then when I ride after about 1 mile feel brakes beginning to seize. Discs hot - if carry on riding the brakes lock completely. Can ease it by loosening the banjo bolt to master cylinder and ride for another mile then same happens. I've checked master cylinder seals and they are in the right way - wide part towards the spring. It feels as if the hydraulics are becoming pressurised and can't flow back into the reservoir.
Any ideas or suggestions on how to work this out much appreciated - Cheers Chris

There is likely air in your system. First thing would be to bleed the entire system.

System bled three times now and brakes feel ok to start - If I lift front wheel off floor it spins ok - brakes work ok and release but then if i pump them a few time can feel the lever stiffen up and wheel eventually locks and does not release unless I open a bleed screw or banjo on the line.

Sounds like the relief port in the master cylinder is plugged. make sure the passages in the bottom of the reservoir are clear of dirt.

Paul said:

Sounds like the relief port in the master cylinder is plugged. make sure the passages in the bottom of the reservoir are clear of dirt.

Click to expand...

+1

OR... if you have an aftermarket fork brace, a bottoming of the forks may have pinched the hose routing clip under the triple tree. Yes, it's happened.

John

Should there be one or two holes in the bottom of the master cylinder - one hole is clean and clear and there is another part drilled one next to it

Yes, two holes, one covered by a press/friction-fit brass deflector plate.

We might be on to something here - second part drilled hole was actually blocked with debris - cleaned it out and there is a small hole through into the piston / cylinder - will let you know how it goes

It is the hole under the deflector spoon that is the return path to the reservoir... make sure it is clear of debris and the brakes should work well.

Hi - both front calipers / pistons stripped cleaned and new seals in - my garage is not ideal conditions but as far as I know they were put back together clean.
The small hole under the deflector plate is now clean but noticed I can make the brakes grip and not fully back off just by pumping the lever. Is it possible the new seals are not clearing the relief hole when the lever is released - mmmm tried removing lever and pressing piston this appears to work brakes don't bind. Maybe plan B is to take a bit off the end of the link between the piston and the lever ?

Right well, how does one apologise on this here forum - further to previous comment I went back to basics on the master cylinder - the problem had to be there somewhere and checked everything over again including the link between lever and piston - it has one large dia rounded end and the other smaller dia rounded end so checked the diagram in the manual and I had it the wrong way round !!!!!! - turned it over and hey presto brakes work, no binding, no overheating they just work as they are supposed to. Looking at it I think the large dia end does not fit flush into the socket in the end of the piston so effectively makes it longer and stops the seal clearing the vent hole which leaves residual pressure in the hydraulics, causes the brakes the rub and overheat etc etc . Thanks everyone and sorry for not checking the details before I got onto you - now a happy bunny back on the road

All's well that ends well! Thanks for the update.

Another thanks for the update. We all learn from our own, as well as others experiences. Although, I've not had your exact problem, I will now always pay closer attention to that detail.

Glad you got it working!