Here's a general outline of the process. Specific steps might vary slightly depending on your exact Aerostar model and engine. Always consult a repair manual specific to your vehicle's year and model for detailed instructions and diagrams.
Tools You'll Need:
* New Master Cylinder: Ensure it's the correct one for your vehicle.
* Wrench Set: Metric and possibly SAE, depending on your van.
* Socket Set: Metric and possibly SAE.
* Pliers: Needle-nose and slip-joint.
* Brake Fluid: DOT 3 or DOT 4, as specified in your owner's manual.
* Catch Pan: To collect old brake fluid.
* Clean Rags or Shop Towels: Brake fluid is corrosive.
* Bleeding Kit: This will help to bleed the brakes after the master cylinder replacement. A vacuum bleeder is easiest, but a manual bleeder and a helper will work.
* Torque Wrench: Essential for tightening bolts to the proper specification.
* Protective Gloves: Brake fluid is corrosive.
* Safety Glasses: Protect your eyes from splashes.
Procedure:
1. Safety First: Engage the parking brake firmly. Disconnect the negative battery cable to prevent accidental electrical shorts.
2. Fluid Drain: Open the brake fluid reservoir cap and use a catch pan to collect the old brake fluid. You might need to siphon some of the fluid out before removing any brake lines to prevent spillage.
3. Disconnect Brake Lines: Carefully loosen the brake lines connected to the master cylinder using the appropriate wrench. Have your catch pan ready to collect the fluid that will spill. Note the order and location of each line so you can reconnect them correctly later. Many use a labeling system.
4. Disconnect Vacuum Booster (if applicable): Some models have a vacuum booster attached to the master cylinder. Disconnect this carefully according to your repair manual.
5. Remove Master Cylinder: Remove the bolts holding the master cylinder to the booster or firewall. This may require some maneuvering.
6. Install New Master Cylinder: Carefully install the new master cylinder, ensuring that it is properly seated and aligned. Tighten the mounting bolts to the specifications in your repair manual. Do not overtighten.
7. Reconnect Brake Lines: Carefully reconnect the brake lines in the same order you disconnected them. Tighten them securely but do not overtighten.
8. Reconnect Vacuum Booster (if applicable): Carefully reconnect the vacuum booster.
9. Fill Brake Fluid Reservoir: Fill the brake fluid reservoir to the "full" line with the correct type of brake fluid.
10. Bleed Brakes: This is crucial to remove air from the brake lines. Use your bleeding kit to bleed the brakes at each wheel, starting with the furthest wheel from the master cylinder. Consult your repair manual for the correct bleeding procedure.
11. Check for Leaks: Inspect all connections for leaks. If you find any, tighten them or replace the faulty parts immediately.
12. Top Off Brake Fluid: Check the brake fluid level in the reservoir and add more if necessary.
13. Test Brakes: Carefully test the brakes before driving. If the brakes feel spongy or unresponsive, you may need to bleed the brakes again.
Important Considerations:
* Repair Manual: A repair manual specific to your 1991 Ford Aerostar is essential. It will provide detailed instructions, diagrams, and torque specifications.
* Professional Help: If you're not comfortable with this repair, take your vehicle to a qualified mechanic. Brake system failures can be dangerous.
* Proper Bleeding: Air in the brake lines can lead to brake failure. Ensure the brakes are properly bled.
This is a general overview. Always consult your vehicle's repair manual for detailed instructions. Improperly installing a master cylinder can lead to brake failure, so proceed with caution and seek professional help if needed.
