I posted on this the other day - basically the front right brake seems clamp istelf on from time to time. Sometimes pulling up the pedal with my foot releases it enough to stop the burning brake smell. I took the wheel and caliper off today to have a look. The wheel would not turn in the pads before I took it off, and I had to pull quite hard to get the caliper off once I had undone the bolts. The only way I could get the pistons to go back was to release fluid form the bleed nipple. Put everything back and bled it, but it seems to be the same.

Someone before suggested that the rod wasn't going back from the master cylinder - any thoughts on why that might happen?; how to check if it is the case?; and, if it is, how to fix it? Or any further ideas?

Thanks.

Previous thread:
http://www.locostbuilders.co.uk/viewthread.php?tid=59840

Okay, If you cannot force the piston back without releasing the some fluid with the nipple then does this apply to all wheels/brakes ?

If so then the master cylinder is not returning far enough to move the seal behind the fluid reservoir hole so you need to shorten the rod/pack out the master cylinder.

If this is only local to this wheel then I suspect that you have some rubbish within the caliper which is acting as a one way valve and falling across the orifice that feeds the caliper.

So, pluck off the other front wheel and see if you can move the pads about, if not the losen the master cylinder bolts to win a bit of free play and try again.

If this fails then remove the caliper and pull out the pistons, wash through and re-assemble.

Regards Mark

I had this on the wifes tin-top, Turned out to be an internal tear in flexi hose acting as a one way valve.

As predicted.


From the sound of it, It is a master cylinder piston not returning problem, probably the mushroom head on the master cylinder pushrod is too large and fouling on the cylinder end washer -- very common problem on one off cars.

It may seem contrary to hydraulic theory that you only get the symptom on only one wheel but it just needs one brake to get hotter than the rest and pad and fluid expands. Easy way to prove it is to open a bleed nipple on another brake in the same hydraulic circuit and see if that also frees the stuck brake.

Thanks again... just one thing though: the car has been on the road for 15 months/2500 miles, so why would it happen now?

There is dirt in master cylinder, there is a very small hole at the bottom of the cylinder that lets fluid back into cylinder. I know because i had this problem.

Should have added above, ig the problem is located only to this one then it may be the brake flexi so crack the joints and work back.

It may not have been noticable before if its the master cylinder if you had air in the brakes as this would have created some give.

Regards Mark