Front Brakes Building Pressure

Question

08 ZX6R, front brakes building pressure on their own. I just finished this restoration. When I got it, the front brake master cylinder was seized up. (Calipers were not) I cleaned and flushed the whole system. Over a week of sitting on stands, the system would build pressure and Lock the front wheel. I’d bleed it and it would be fine. So I rebuilt the master cylinder with all new internals. It would still build pressure but nowhere near as fast or bad. (Maybe 3 weeks but could still move the front wheel) I bled the system last night. I just took it for its first test ride and after about a mile it completely locked the front brakes. I had to open the bleeder to get it back home. What is causing this?


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Nick Tea 3 years 23 Answers 1043 views 0

Answers ( 23 )

  1. Bad. Caliper

  2. Ryan, the rear caliper the piston barely moves correct ? I know it moves but when I was looking over my brakes mine only moved maybe an 1/8″

    • When you press the pedal wheel stops when released should free spin but if there is any bit of air or the fluid seeps by a seal it will lock up

  3. Oem levers? Or aftermarket?

  4. I had the same issue and it was the aftermarket lever, put the oem on and problem was fixed

  5. Have it checked out at a shop.one bubbly trapped in the breaks messed my buddy up at 30mph when it lockednup

  6. whoever put china levers on the bike caused the issue.

  7. Swollen cylinder valve seals ?

  8. Bad seal on the master or caliper, its allowing fluid in past the master and down to the caliper without being engaged, the only problem it could be is a bad seal or check valve

    • Same as what I thought, the brake fluid cant flow back to the reservoir thats why it keeps building up pressure, could be a bad seal .. try pressing the lever a hundred times to see if the brake jams or not

  9. Bad lines……rubber inside the lines dry rots and flakes….acts like a check valve or one way valve…..letting fluid go to calipers but not return. Last thing I ever thought it would be on my bike but sure as hell was…..hope this helps bro

  10. bad cheap shitty levers they should be banned !!!

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