That being said, if you're determined to attempt it yourself, here's a general outline. Remember this is not a comprehensive guide and omits many crucial safety precautions and details. Failure to follow proper procedures could result in catastrophic brake failure.
1. Safety First:
* Park on a level surface, engage the parking brake (if it still works), and chock the wheels. This is critical even if your brake lines are compromised.
* Wear safety glasses and gloves.
* Obtain a complete repair kit containing the correct size and type of brake line tubing, double flare tool, tubing cutter, and appropriate fittings. You'll need to know the exact size of the line. Incorrect parts will lead to failure.
* Have a helper. This is very difficult to do alone.
2. Locating the Break:
* Carefully inspect the brake lines to locate the break. Look for leaks, rust, or damage.
3. Repairing the Line (General Steps):
* Drain brake fluid: Before disconnecting any lines, you must drain the brake fluid from the master cylinder reservoir.
* Disconnect the broken line: Carefully disconnect the brake line at the point of the break using the appropriate wrenches. Be prepared for some brake fluid leakage.
* Measure and cut new brake line: Measure the length of the replacement line needed. Use a tubing cutter to ensure a clean, square cut.
* Flare the ends: Use the double flare tool to create the correct flare on both ends of the new brake line segment. This is critical for a proper seal. An improperly flared line will leak and fail.
* Connect the new line: Carefully connect the new section of brake line using the correct fittings. Tighten the fittings securely to the proper torque specifications (found in a repair manual).
* Reconnect the lines: Reconnect the brake lines to the original system.
* Bleed the brakes: This is crucial. You must bleed the brakes completely to remove any air that entered the system during the repair. This requires a helper and a brake bleeder kit. Refer to your owner's manual for the proper bleeding procedure. This is typically done starting at the furthest wheel from the master cylinder and working your way closer.
4. Testing:
* Carefully test the brakes: After bleeding the brakes, test them thoroughly in a safe, controlled area. Begin with light braking, then gradually increase pressure. Listen carefully for any leaks or unusual sounds. If you feel anything is wrong, stop immediately.
What you absolutely need:
* Repair manual specific to your 1999 GMC Sierra: This will give you the correct specifications, diagrams, and torque values.
* Correct size and type of brake line tubing: This is crucial for safety and proper function. Using the wrong type can lead to catastrophic failure.
* Double flare tool: A poorly flared line will leak and is extremely dangerous.
* Tubing cutter: A clean cut is necessary for a proper flare.
* Appropriate fittings: Ensure compatibility with your brake lines.
* Brake fluid: Use the correct type specified in your owner's manual.
* Brake bleeder kit: This is essential to remove air from the brake lines.
* Wrenches: The correct size to handle the fittings and connectors.
Again, this is a simplified overview and omits crucial safety and technical details. Attempting this repair without proper knowledge and tools is extremely risky. Take your vehicle to a qualified mechanic. Your safety is paramount.
