mx5cartalk.com

Ever since i've had my NB8A the brakes have never impressed me. I have bled the brakes about a thousand times, installed braided lines, greased the slide pins, and adjusted rear calipers so they are almost dragging. All of which has resulted in no significant improvement. I have noticed however, with the handbrake applied 30% the pedal feel is improved significantly. Also, when I push the thing that floats inside the master cylinder, black misty stuff comes out.

After all this I think the master cylinder may need replacing, would you blokes agree? Any advice would be appreciated. Currently running QFM HPX Brake Pads

sounds like the master cylinder or brake booster has a leak, probably a hole in the diaphragm inside. you change them both as a whole anyways

The seals around the pistons in the master cylinder are deteriorating. That's the black misty stuff you see - perished rubber.

As soon as I see that starting to happen on any car of mine I replace or rebuild the master cylinder. Soft pedal then goes away.

Cool cool, this has been helpful. I'll look into a new one/rebuild.

On an aside, my gasket around the reservoir cap was deteriorating. This caused misty rubber to dirty my fluid.