1995 GMC Jimmy Owner's Manual - Page 267

Brakes Brake Master Cylinder Your brake master cylinder is here. It is filled with DOT-3 brake fluid. There are only two reasons why the brake fluid level in your master cylinder might go down. The first is that thebrake fluid goes down to an acceptable level during normal brake lining wear. When new linings put in, the are fluid level goes back up. The other reason is that fluid 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, 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 youget new brake linings. You should add (or remove) brake fluid, as necessary, only when work is done onthe brake hydraulic system. Refer to the Maintenance Schedule to determine when to check your brake fluid. See "Periodic Maintenance Inspections'' in the Index. 6-27