1. Verify Bleeding Procedure:
* Correct Bleeder Order: Did you bleed the brakes in the correct order? This is crucial. Generally, it's a diagonal pattern (e.g., Right Rear, Left Front, Right Front, Left Rear). Consult your repair manual for the *precise* order for your specific model. Incorrect order can trap air.
* Proper Bleeding Technique: Did you use a helper to keep the brake pedal depressed? Did you open the bleeder valves slowly and completely close them before releasing the pedal? Did you keep the master cylinder reservoir topped off with the correct brake fluid? Insufficient fluid leads to air ingestion.
* Multiple Bleed Cycles: Sometimes, even with correct procedure, air bubbles can be stubborn. Try bleeding each caliper multiple times until clear fluid comes out consistently.
2. Check for Obvious Leaks:
* Master Cylinder: Inspect the new master cylinder for leaks around its connections. A faulty master cylinder itself is possible, though less likely given you just installed it.
* Brake Lines and Hoses: Examine all brake lines and hoses for any cracks, bulges, or leaks. Even small leaks can significantly compromise braking performance. Look under the car closely.
* Wheel Cylinders/Calipers: Check the wheel cylinders (rear brakes) or calipers (front brakes) for leaks. These are common points of failure. Look for brake fluid dripping or staining.
3. Air Still in the System (Beyond Basic Bleeding):
* Vacuum Bleeding: If you suspect air is still trapped deep within the system, consider vacuum bleeding. This method uses a vacuum pump to draw fluid and air out more effectively than gravity bleeding. Many auto parts stores rent vacuum bleeding tools.
* Pressure Bleeding: Similar to vacuum bleeding, pressure bleeding uses compressed air to force fluid through the system, removing stubborn air pockets. This also requires specialized equipment.
4. Consider These Less Likely (But Possible) Issues:
* Proportioning Valve: This valve controls brake pressure distribution between the front and rear brakes. A faulty valve can lead to ineffective braking.
* Brake Booster: The booster assists in brake pedal pressure. A malfunctioning booster will result in a very hard brake pedal and poor braking. This is less likely to cause complete failure immediately after a master cylinder replacement, but it's still possible.
* ABS System (If Equipped): If your Town & Country has anti-lock brakes (ABS), a problem within the ABS system could affect braking. This often requires specialized diagnostic tools.
* Faulty New Master Cylinder: While unlikely, there's a small chance the new master cylinder is defective.
5. Professional Help:
If you've gone through all the above steps and still have no brakes, seek professional help immediately. Driving a vehicle with faulty brakes is extremely dangerous. A qualified mechanic has the tools and expertise to diagnose and repair the problem accurately.
Important Safety Note: Brake failure is a serious safety issue. Do not attempt to drive the vehicle until the problem is resolved. Have it towed to a repair shop.
