Q: Brakes lose pressure sometimes

asked by on December 06, 2016

Sometimes when hitting the breaks the pedal will go to the floor. I pump them and the pressure back up. Sometimes its hard, sometimes squishy. When the pressure is there the pedal does not sink.

Your brake issues can be singular or possible twofold. When the brake pedal goes too low, or to the floor, but firms up if pumped, that indicates that the primary seal in the master cylinder has failed. Pumping the brakes allows the secondary seal to produce some pressure. By that alone, I suggest replacing the brake master cylinder.

A ’hard" brake pedal can indicate a vacuum issue with the power brake booster. The booster itself may be failing - possible if brake fluid is leaking from the master cylinder into the booster and will not be a visible leak until the master cylinder is removed from the booster. Also, the booster may not be receiving the proper amount of vacuum from the engine. This can be due to the vacuum hose being partially collapsed internally, or the vacuum check valve not functioning properly.

I would recommend the master cylinder replacement - which would include bleeding the entire brake system. If the pedal continues to feel "hard" after replacement, a certified technician can further inspect the system to determine why the brake pedal is hard.

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