This outlines the general procedure. Specifics may vary slightly depending on your van's configuration. Always consult a repair manual specific to your 1991 Chevy Astro van for detailed diagrams and torque specifications.
I. Preparation:
1. Safety First: Wear safety glasses and gloves. Properly support the vehicle on jack stands. Never work under a vehicle supported only by a jack.
2. Gather Supplies: You'll need new brake lines (get the correct length and type from an auto parts store – specifying your van's year and model is crucial), tubing cutter, flaring tool (double flaring is recommended), brake line wrench(es) (for various sizes), double-flare nut, brake fluid, a funnel, rags, and possibly a helper. A brake line bending tool will also greatly simplify the process, preventing kinks. A pressure bleeder is recommended for easier bleeding after replacement.
3. Drain Brake Fluid: Open the bleeder valve on each wheel cylinder to drain the old brake fluid into a container. This reduces the mess and the amount of air you need to purge from the system.
4. Locate and Identify Lines: Carefully examine the existing brake lines to understand their routing. Take pictures or make sketches.
II. Removal of Old Lines:
1. Disconnect Lines: Carefully disconnect the brake lines from the various components (master cylinder, proportioning valve, wheel cylinders/calipers). Use the correct wrenches to avoid rounding off the nuts. Be prepared for some brake fluid leakage.
2. Remove Old Lines: Once disconnected, carefully remove the old brake lines. Take note of their routing to help with installation of the new lines. You may need to use a tubing cutter to cut sections.
III. Installation of New Lines:
1. Cut and Flare: Measure and cut the new brake lines to the correct lengths. Use a flaring tool to create double flares on the ends that will connect to fittings. Ensure flares are clean and undamaged.
2. Routing: Carefully route the new brake lines, replicating the routing of the old lines as closely as possible. Avoid sharp bends that could restrict fluid flow. A bending tool is invaluable here.
3. Connect Lines: Connect the new brake lines to the various components using appropriate nuts and fittings. Tighten them securely but avoid over-tightening.
4. Leak Check: Before bleeding the system, carefully inspect all connections for leaks. Use soapy water to check for bubbles which indicate leaks. Repair any leaks immediately.
IV. Bleeding the Brakes:
1. Bleeding Procedure: Bleed the brakes to remove air from the system. This is typically done by opening the bleeder valve on each wheel while someone pumps the brake pedal. A pressure bleeder makes this process significantly easier and more efficient. Refer to your repair manual for the correct bleeding sequence.
2. Check Brake Pedal: After bleeding, check the brake pedal for firmness. If the pedal feels spongy, you may need to bleed the system again.
V. Final Checks:
1. Leak Check (Again): Inspect all connections one more time for leaks.
2. Test Drive: Take a short test drive to verify the brakes are functioning correctly. Be cautious and test at low speeds at first.
Important Notes:
* Proportioning Valve: Be extra careful when working around the proportioning valve. Incorrect adjustments can severely impair braking performance.
* ABS (If Equipped): If your Astro has Anti-lock Braking System (ABS), the process is significantly more complex and requires specialized tools and knowledge. Do not attempt this without the necessary expertise.
* Repair Manual: A repair manual is absolutely essential for this project. It will provide detailed diagrams, torque specifications, and bleeding procedures.
This is a general overview. Again, this is a complex repair. If you lack the experience or confidence, take your vehicle to a qualified mechanic. Improper brake repair can be extremely dangerous.
