1. Verify the Repair:
* Leak Check: Before bleeding, double-check your brake line connection. Ensure it's tight and there are no leaks. A small leak can introduce air constantly.
* Proper Routing: Make sure the new brake line is routed correctly, avoiding sharp bends that could trap air.
2. Bleeding Procedure:
You'll need a helper and the following:
* Brake Bleeder Wrench: Fits the bleeder valve on your calipers.
* Clear Tubing: To connect to the bleeder valve and collect brake fluid.
* Container: To catch the used brake fluid.
* New Brake Fluid: DOT 3 or DOT 4, as specified in your owner's manual. Never mix different types of brake fluid.
* Jack and Jack Stands (Crucial): Safely support the truck. Working on a vehicle that's not properly supported is extremely dangerous.
The Bleeding Process:
The general order for bleeding brakes is to start with the furthest wheel from the master cylinder and work your way towards it. For a rear-wheel-drive 1995 GMC pickup, this usually means:
1. Passenger-side rear: Attach the hose to the bleeder valve, place the other end in the container, and have your helper pump the brake pedal firmly several times. Then, have them hold the pedal down while you open the bleeder valve slowly. Close the bleeder valve before your helper releases the pedal. Repeat this process several times until you see only a steady stream of brake fluid with no bubbles.
2. Driver-side rear: Repeat the process for the driver-side rear wheel.
3. Passenger-side front: Follow the same process.
4. Driver-side front: Finally, bleed the driver-side front wheel.
Important Considerations for Rear Brakes:
* Gravity Bleed: If you can't find a helper, you can try a gravity bleed. This involves raising the rear of the vehicle to ensure the calipers are higher than the master cylinder. Open the bleeder valves and let the fluid drain slowly. This is less effective than pressure bleeding, but may help in some cases. However, make sure it is still safe and the vehicle is properly secured.
* Vacuum Bleeder: A vacuum bleeder is a tool that creates a vacuum to draw fluid and air out. This method is very efficient and often necessary for complete bleeding. Rent one from an auto parts store if you're struggling.
* Pressure Bleeder: A pressure bleeder is attached to the master cylinder and applies pressure to the system, forcing the air out more effectively than gravity. It's highly recommended.
* Multiple Bleeds: You might need to repeat the bleeding process several times to ensure all air is removed. If you're unsure, have a mechanic perform the bleed.
3. Check for Air in the Master Cylinder:
If you're still having trouble after multiple bleed cycles, there might be air trapped in the master cylinder. This is less common after just replacing a brake line but is possible. This requires a more advanced procedure and might be best left to a professional.
4. Inspect for Other Problems:
* Clogged lines: If a line is partially clogged, it can create issues similar to air in the lines.
* Faulty caliper: A damaged or seized caliper piston might prevent proper bleeding.
Safety First: Always wear safety glasses when working with brake fluid. Brake fluid is corrosive and can damage paint and other materials. If you're uncomfortable with any part of this process, consult a qualified mechanic. Improperly bled brakes are extremely dangerous.
