However, if you're determined to attempt the repair yourself, here's a general outline. Remember, this is a *general guide* and specific steps may vary slightly depending on your Aerostar's exact configuration. Always consult a repair manual specific to your vehicle's year and model for precise instructions and torque specifications.
1. Safety First:
* Disconnect the negative battery terminal. This prevents accidental short circuits.
* Gather your tools: You'll need wrenches (metric), sockets, a brake bleeder kit, a new master cylinder (ensure it's the correct one for your Aerostar), and possibly a C-clamp. You'll also likely need a helper.
* Work in a well-ventilated area. Brake fluid is corrosive and harmful if ingested or inhaled. Wear safety glasses and gloves.
* Support the vehicle securely. Use jack stands, never rely solely on a jack.
2. Draining the Brake Fluid:
* Locate the brake lines connected to the master cylinder.
* Open the bleeder valves on each wheel cylinder (usually a small valve on top of each caliper or wheel cylinder).
* Have a helper pump the brake pedal a few times to force fluid out of the lines.
* Carefully collect the fluid in a container. Brake fluid is corrosive, so use a container specifically for it.
3. Removing the Old Master Cylinder:
* Disconnect the brake lines: This is crucial and requires care. Use a wrench to loosen the fittings and then use a flare nut wrench to carefully unscrew them. Have a helper plug the lines with rubber caps or appropriately sized bolts to prevent fluid loss.
* Disconnect the brake booster: This usually involves removing bolts holding the booster to the firewall.
* Remove the master cylinder: This typically involves removing bolts or clamps securing the master cylinder to the booster.
4. Installing the New Master Cylinder:
* Install the new master cylinder: Carefully align and install the new master cylinder in the reverse order of removal. Ensure a good seal is made.
* Reconnect the brake lines: Tighten the fittings carefully to the correct torque specifications (found in your repair manual). Do not overtighten.
* Reconnect the brake booster.
* Bleed the brakes: This is critical to remove air from the brake lines. Use your bleeder kit, starting with the furthest wheel from the master cylinder and working your way closer. Have your helper pump the brake pedal as you open and close the bleeder valve on each caliper or wheel cylinder. Repeat until no air bubbles are visible in the fluid.
5. Testing the Brakes:
* Carefully pump the brakes several times to build pressure.
* Test the brakes in a safe, open area at low speeds.
* Check for leaks: Inspect all connections for leaks.
* If any problems are found, immediately stop driving and seek professional help.
Important Considerations:
* Proportional Valves: Some Aerostars might have a proportional valve related to the master cylinder. Consult your repair manual to understand its function and how to handle it during the replacement process.
* Brake Fluid Type: Use the correct type of brake fluid specified for your Aerostar. Using the wrong fluid can damage the system.
* Bleeding the Brakes Properly: Improper bleeding can lead to spongy brakes or brake failure. If you're unsure, seek professional help.
Again, this is a simplified overview. Replacing a master cylinder is a complex task with the potential for serious consequences if done incorrectly. It's strongly recommended that you consult a detailed repair manual and, if you lack experience, take your vehicle to a qualified mechanic. Your safety and the safety of others depend on it.
