* Brake Caliper Issues: This is the most common cause. A seized caliper piston will constantly apply pressure to the brake pads, even when you're not braking. This could be due to:
* Rust and corrosion: Salt, moisture, and time can cause the caliper piston to seize.
* Stuck caliper slider pins: These pins allow the caliper to move freely. If they're seized, the caliper can't retract.
* Damaged caliper seals: Internal seals can fail, allowing fluid to leak or preventing the piston from retracting properly.
* Brake Lines: A restricted or damaged brake line can cause excessive pressure to build up in the front brakes. Look for leaks, kinks, or rust damage.
* Master Cylinder: While less common, a failing master cylinder can send uneven pressure to the brakes, potentially locking up the fronts. A leak or internal failure is possible.
* Vacuum Booster: A malfunctioning vacuum booster can cause excessive brake pedal pressure, leading to brake lockup. This is less likely to cause *only* the front brakes to lock, but it's possible.
* Parking Brake Cable: Make absolutely sure your parking brake isn't engaged. A malfunctioning or stuck parking brake cable could be the cause.
* ABS Issues (Less Likely): While less likely to cause complete lockup, a problem with the Anti-lock Braking System (ABS) could contribute. This is usually accompanied by an ABS warning light.
What to do:
1. Safety First: Do not drive the truck. Have it towed to a safe location or a repair shop.
2. Check the Obvious: Ensure the parking brake is completely disengaged.
3. Inspect the Front Brakes: If you're comfortable doing so (and have the proper safety gear), visually inspect the front brake calipers for signs of rust, leaks, or damage. Check the brake pads for excessive wear.
4. Professional Help: This is likely beyond a simple DIY fix. Take your truck to a qualified mechanic for diagnosis and repair. They have the tools and expertise to diagnose the problem accurately and safely.
Do not attempt to fix this yourself unless you have significant automotive experience and the proper tools. Improper brake repair can be extremely dangerous.
