1996 Chevrolet Astro Owner's Manual - Page 237

Brakes Brake Master Cylinder Your brake master cylinder is here. It is filled with DOT-3 brake fluid. There are only two reasons the brake fluid level in your master cylinder why might go down. The firstis that the brake fluid goesdown to an acceptable level during normal brake lining wear. When new linings areput in, the fluid level goesback up. The otherreason 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, or won't work at all. So, it isn't a good idea to "topoff' your brake fluid. Adding brake fluid won't correct a leak.If you add fluid when your linings areworn, then you'll have too much fluid when you get new brake linings. You should add (or remove) brake fluid, asnecessary, only when work is done on the brake hydraulic system. A CAUTION: If you have too much brake fluid, it can spill engine. The on the fluid will burn the engineis hot enough.You or others could if be burned, and your vehicle could be damaged. Add brake fluid only when work is done on the brake hydraulicsystem. Refer to the Maintenance Schedule to determine when to check your brake fluid. See "PeriodicMaintenance Inspections" in the Index. 6-29