1995 GMC Safari Owner's Manual - Page 235

Brakes Brake Master Cylinder Your brake master cylinder is here. It is 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 anacceptable level during normal brake lining wear. When newlinings are put in, the fluid level goes back up. The other reason is thatfluid is leaking out 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, or won't work at 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 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. Refer to the Maintenance Schedule todetermine when to check your brake fluid. See "Periodic Maintenance Inspections" in the Index. 6-23