1999 GMC Sonoma Owner's Manual - Page 270

yellowblue Checking Brake Fluid You can check the brake fluid without taking off the cap. What to Add When you do need brake fluid, use only DOT-3 brake fluid. Refer to "Recommended Fluids and Lubricants" in the Index. Use new brake fluid from a sealed container only. Always clean the brake fluid reservoir cap and the area around the cap before removing it. This will help keep dirt from entering the reservoir. CAUTION: Just look at the brake fluid reservoir. The fluid level should be above MIN. If it isn't, have your brake system checked to see if there is a leak. After work is done on the brake hydraulic system, make sure the level is above the MIN but not over the MAX mark. With the wrong kind of fluid in your brake system, your brakes may not work well, or they may not even work at all. This could cause a crash. Always use the proper brake fluid. 6-32