Pontiac 2003 Vibe - Manual (Page 283)

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So, it isn’t a good idea to “top off” your brake fluid.
Adding brake fluid won’t correct a leak. If you add fluid
when your linings are worn, then you’ll have too much
fluid when you get new brake linings. You should add
(or remove) brake fluid, as necessary, only when work is
done on the brake hydraulic system.
CAUTION:
If you have too much brake fluid, it can spill on
the engine. The fluid will burn if the engine is hot
enough. You or others could be burned, and your
vehicle could be damaged. Add brake fluid only
when work is done on the brake hydraulic
system.
United States Canada
When your brake fluid falls to a low level, your brake
warning light will come on. See “Brake System Warning
Light” in the Index.