2008 GMC Envoy Owner's Manual - Page 332

Brakes Brake Fluid The brake master cylinder reservoir is filled with DOT-3 brake fluid. See Engine Compartment Overview on page 5-12 for the location of the reservoir. It is not a good idea to top off the brake fluid. Adding brake fluid will not correct a leak. If fluid is added when the linings are worn, there will be too much fluid when new brake linings are installed. 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. See "Checking Brake Fluid" in this section. Refer to the Maintenance Schedule to determine when to check your brake fluid. See Scheduled Maintenance on page 6-4. There are only two reasons why the brake fluid level in the reservoir might go down. The first is that the brake fluid goes down to an acceptable level during normal brake lining wear. When new linings are put in, the fluid level goes back up. The other reason is that fluid is leaking out of the brake hydraulic system. If it is, you should have the brake hydraulic system fixed, since a leak means that sooner or later the brakes will not work well. 5-38