1. Master Cylinder Issues:
* Low fluid: Even with new brakes, the master cylinder needs sufficient brake fluid. Check the fluid level in the master cylinder reservoir. If low, there's a leak somewhere in the system (master cylinder, wheel cylinders, lines, etc.).
* Master cylinder failure: The master cylinder itself might be faulty (internal leak or piston sticking). This is more likely if the fluid level is dropping.
* Air in the lines: Air in the brake lines prevents proper pressure buildup. This is a common issue after brake work. Bleeding the brakes thoroughly is essential.
2. Wheel Cylinder/Caliper Problems (depending on drum or disc brakes):
* Wheel cylinder/Caliper failure (rear drum brakes): A faulty wheel cylinder might be leaking internally or not extending its pistons properly. This is a common problem on older vehicles.
* Caliper piston sticking (front disc brakes): A seized or sticking caliper piston prevents the brake pad from contacting the rotor.
3. Brake Lines and Hoses:
* Leaks: Check all brake lines and hoses for leaks. Even a small leak can significantly reduce braking power.
* Clogged lines: A blockage in the brake lines can prevent fluid from reaching the wheels. This is less common but possible.
4. Proportioning Valve (if equipped):
* Malfunction: The proportioning valve regulates brake pressure between the front and rear brakes. A faulty valve can cause braking imbalance or complete failure.
5. Brake Booster:
* Vacuum leak: A vacuum leak in the booster's vacuum line prevents proper assistance from the booster, resulting in weak or no braking.
6. Incorrect Installation:
* Lines improperly connected: A simple mistake during installation can render the brakes useless. Double-check all connections.
* Brake components installed incorrectly: Improper installation of calipers, wheel cylinders, or other parts.
7. Other less likely, but possible causes:
* Parking brake engaged: Sounds obvious, but easily missed.
* Incorrectly sized or type of brake parts: Using the wrong parts can lead to malfunctions.
Troubleshooting Steps:
1. Check brake fluid level: This is the first and easiest check.
2. Check for leaks: Inspect all brake lines, hoses, and wheel cylinders/calipers carefully.
3. Bleed the brakes: This is crucial to remove any air that might be trapped in the system. Follow the proper bleeding procedure for your vehicle.
4. Check the master cylinder: Look for leaks or signs of malfunction. A professional inspection might be needed.
5. Inspect wheel cylinders/calipers: Check for leaks, sticking pistons, or other problems.
6. Verify correct installation: Double-check all connections and components.
If you're not comfortable working on brakes yourself, take your truck to a qualified mechanic. Brake failure is extremely dangerous. Don't drive the vehicle until the problem is fixed.
