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Yes, that is a problem. If you used the vehicle since you did this, the system should be flushed and inspected by a trained individual. If it wasn't used and the brakes never applied after the mistake, remove everything from the master cylinder, wipe everything clean, and refill with brake fluid. I would still have it looked at for safety.
Let me know if you have other questions.
Wednesday, July 31st, 2019 AT 6:34 AM