1994 Chevrolet Blazer Owner's Manual - Page 264

Brakes Brake Master Cylinder Your brake master cylinder is here. Itis filled with DOT-3 brake fluid. There areonly two reasons why the brake fluid level in your master cylinder might go down. The first is that the brake fluid goes down to an acceptable the level during normal brake lining wear. When new linings are put in, fluid level goes back up. The other reason is that fluid is leakingout of the brake system. If it is, you should have your brake system fixed, since a leak means that sooner or later your brakes won't work well, won't work at or all. 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 yourlinings 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 isdone on the brake hydraulic system. Refer to the Maintenance Schedule to determine when to check your brake fluid. See "Periodic Maintenance Inspections" in the Index. 6-28