* Brake Line Restriction: A partially clogged or kinked brake line leading to the left front caliper could be restricting fluid flow. When the brake pedal is released, the fluid doesn't return to the reservoir as quickly, causing the caliper piston to stick. Inspect the brake line for kinks, rust, or internal blockage. You might need to bleed the brakes thoroughly after replacing a section of line if damage is found.
* Caliper Piston Problem (Even with a New Caliper): While you've replaced the caliper, there's a small chance the new caliper itself is faulty. Though rare, it's possible the piston isn't retracting fully.
* Brake Hose Problem: The flexible brake hose connecting the hard line to the caliper could be internally collapsing or swollen, preventing proper fluid return. This is common as hoses age and degrade. A visual inspection may reveal bulging or cracking, but a pressure test might be needed for a definitive diagnosis.
* Improper Bleeding: Air trapped in the brake line after replacing the master cylinder can cause sticking. Make absolutely sure you've properly bled the brakes, following the correct procedure for your vehicle. In some cases, a vacuum bleeder might be necessary to remove stubborn air pockets.
* Parking Brake Cable: Although less likely if the parking brake is released, a sticking or partially engaged parking brake cable could contribute to the sticking. Inspect the cable and its mechanism for free movement.
* Wheel Bearing Issues: A severely seized wheel bearing can put enough pressure on the brake components to cause the pads to stick, even after replacing parts. This is a more serious issue and often involves abnormal noise or play in the wheel.
* Contamination: Something might have contaminated the brake system during the repair. Dirt, debris, or even the wrong type of brake fluid can affect the system's performance.
Troubleshooting Steps:
1. Visually Inspect: Thoroughly examine the brake line, brake hose, and caliper for any damage, swelling, or corrosion.
2. Bleed the Brakes: Bleed the brakes again, making sure to follow the correct order (usually starting with the furthest wheel from the master cylinder). A helper is usually needed for this process.
3. Pressure Test: If the problem persists, a pressure test of the brake system can pinpoint leaks or restrictions. This requires specialized equipment.
4. Check for Free Movement: Make sure the caliper piston moves freely and retracts completely when the brakes are released.
5. Inspect the Parking Brake: Ensure the parking brake cable is not binding or partially engaged.
6. Check Wheel Bearing: Inspect the wheel bearing for play or excessive resistance.
If you are not comfortable performing these checks or repairs yourself, it's best to take your vehicle to a qualified mechanic. A persistent sticking brake is a safety hazard and requires professional attention to ensure it's fixed correctly.
