Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 333 (DISC BRAKES)SYMPTOM TESTSBRAKE FLUID LOSS
1999 GMC Forward Control 5.7 R, Automatic
Brake Fluid Loss
1999 GMC Forward Control 5.7 R, AutomaticSECTION Brake Fluid Loss
WARNING: This page is about a different car, the 2003 Pontiac Grand Prix. However, it is still accessible from the selected car via links, so may be relevant.
- Were you sent here from the Hydraulic Brake Symptom table? If so, go to next step. If not, go to DIAGNOSTIC STARTING POINT under TROUBLE SHOOTING.
- Inspect the hydraulic brake system for proper operation. See HYDRAULIC BRAKE SYSTEM DIAGNOSIS under SYSTEM TESTS. Did you find and correct a condition? If so, go to step 6 . If not, go to next step.
- Inspect the disc brake system for proper operation. See DISC BRAKE SYSTEM DIAGNOSIS under SYSTEM TESTS. Did you find and correct a condition? If so, go to step 6 . If not, go to next step.
- Separate the master cylinder from the power brake booster. DO NOT disconnect any brake pipes. See MASTER CYLINDER under REMOVAL & INSTALLATION. Inspect the rear of the master cylinder for a brake fluid leak. Inspect for brake fluid in the power brake booster. Did you find a brake fluid leak? If so, go to next step. If not, go to DIAGNOSTIC STARTING POINT under TROUBLE SHOOTING.
- Replace the brake master cylinder and the power brake booster. See MASTER CYLINDER & POWER BRAKE BOOSTER under REMOVAL & INSTALLATION. After repairs are complete, go to next step. If not, go to step.
- Install or connect components that were removed or disconnected during diagnosis. Road test the vehicle to confirm proper operation. See BRAKE SYSTEM VEHICLE ROAD TEST under TROUBLE SHOOTING. Is the condition still present? If so, go to step 2 . If not, system is okay.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.