Possible Causes:
* Master Cylinder Failure: This is a primary component. A failing master cylinder won't build pressure, leading to no brakes or very weak brakes. Look for leaks around the cylinder.
* Brake Booster Failure: The booster assists pedal pressure. A failed booster will require excessive pedal force or result in no braking. You might notice a very hard brake pedal.
* Low Brake Fluid: Check the brake fluid reservoir (usually a clear container under the hood). Low fluid indicates a leak somewhere in the system. Never top off low fluid without investigating the leak first.
* Brake Lines: Rust or damage to brake lines can cause leaks and loss of pressure. Inspect the lines carefully for leaks, rust, or kinks.
* Wheel Cylinders/Caliper Issues (Rear Drum Brakes/Front Disc Brakes): These components work to squeeze the brake pads against the rotors (disc) or drums (drum). Leaks or seized pistons in these components will result in poor or no braking on the affected wheel(s).
* ABS System (Anti-lock Braking System) Failure: While less likely to completely eliminate braking, a faulty ABS module or sensor can interfere with braking performance. The ABS light on the dashboard might be illuminated.
* Proportioning Valve: This valve regulates brake pressure between front and rear brakes. A faulty valve could cause an imbalance and reduce overall braking power.
Troubleshooting Steps (Do these with extreme caution, ideally with someone assisting):
1. Check Brake Fluid: First and foremost, check the brake fluid level in the reservoir. Low fluid indicates a leak somewhere in the system. If low, don't drive the truck; have it towed.
2. Inspect Brake Lines: Carefully inspect all brake lines for leaks, rust, or damage. Look for wet spots or corrosion.
3. Pump the Brake Pedal: With the engine OFF, pump the brake pedal several times. If the pedal goes to the floor and stays there, there's a serious problem, likely with the master cylinder or a major leak.
4. Check for Leaks: Look for brake fluid leaks around the master cylinder, wheel cylinders/calipers, and brake lines.
5. Listen for Air Leaks: Air in the brake lines can severely compromise braking. You may hear hissing sounds near the master cylinder or wheel cylinders if there's a leak.
What NOT to Do:
* Drive the vehicle: This is extremely dangerous. Have it towed to a qualified mechanic.
* Attempt major repairs yourself: Unless you have extensive experience with brake systems, attempting repairs yourself could worsen the situation and create a significant safety risk.
Next Steps:
Have the truck towed to a qualified mechanic or repair shop. They have the tools and expertise to diagnose the problem accurately and perform the necessary repairs safely. Explain the situation clearly to the mechanic; this is a critical safety issue. Don't attempt to drive it again until it's repaired.
