2007 GMC Acadia Owner's Manual - Page 421

Brakes Brake Fluid The brake master cylinder reservoir is filled with DOT-3 brake fluid. See Engine Compartment Overview on page 396 for the location of the reservoir. So, it is not a good idea to top off the brake fluid. Adding brake fluid will not correct a leak. If you add fluid when the linings are worn, then you will 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. {CAUTION: If your vehicle has 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. When the brake fluid falls to a low level, the brake warning light comes on. See Brake System Warning Light on page 222. 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 system. If it is, you should have the brake system fixed, since a leak means that sooner or later the brakes will not work well. 421