This is probably a very simple question, but I was just poking around the engine bay and checking the fluid levels of the various reservoirs. I then opened the brake fluid one and I remember reading that be very careful not to get any air into the brake lines and will need bleeding if that occurs.

So am I worrying about nothing or should I be planning on bleeding my brakes?


Absolutely not. The reservoir holds 'the excess' brake fluid, and bubbles in the reservoir will float to the top.

You would need to bleed the brakes, however, if you had taken the reservoir off and/or drained it completely and pushed the brake pedal. This would include if you had a leak and one (or both) sides of the reservoir was completely empty. 'Air in the lines' only is a problem once the air is past the master cylinder.

Just taking the top off to inspect/add brake fluid does not necessitate bleeding.

  • Very insightful and much appreciated.
    – DanP
    Aug 29 '12 at 15:35

In my experience (which is on older cars and motorcycles), no - you should be fine.

Yes it is true that air in the brake lines is bad news, so if you had a leak somewhere along a line or at the bottom or the reservoir thats drawing air in along with fluid that would necessitate a bleed. But since you just opened it from the top it should be fine. Just ensure the lid is back on securely.

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