Tools You'll Likely Need:
* Socket set (metric)
* Wrenches (metric)
* Screwdrivers (Phillips and flathead)
* Brake cleaner
* Vacuum pump or gauge (to test the new booster)
* New brake booster
* New vacuum hose(s)
* Possibly a helper
General Steps:
1. Safety First: Disconnect the negative battery terminal. This prevents accidental short circuits.
2. Access the Booster: The brake booster is typically located on the firewall, behind the brake pedal. You'll likely need to remove some components to access it easily. This may include:
* Removing the air cleaner assembly for better access.
* Removing the master cylinder from its mounting bracket (possibly). This might be necessary to get to the booster's mounting bolts.
* Removing the brake pedal assembly (possibly) depending on the clearance required.
3. Disconnect Components:
* Carefully disconnect the vacuum line from the brake booster.
* Disconnect the pushrod from the booster to the master cylinder. Take note of its position for proper reinstallation. You may need to mark it.
* Disconnect any electrical connectors if present.
4. Remove the Brake Booster: This usually involves removing several bolts that secure the booster to the firewall. These bolts can be tricky to reach, requiring extensions and swivel sockets. Be patient and methodical.
5. Install the New Brake Booster:
* Carefully install the new brake booster, ensuring it's properly aligned with the mounting holes.
* Tighten the mounting bolts to the manufacturer's specifications (refer to your repair manual).
* Reconnect the pushrod to the master cylinder, ensuring it's properly aligned and at the correct length (as noted in step 3).
* Reconnect the vacuum line to the booster.
* Reconnect any electrical connectors.
6. Bleed the Brakes: After reinstalling the master cylinder (if removed), you must bleed the brakes to remove any air that may have entered the system during the repair. This is crucial for proper braking function. Use a helper to pump the brake pedal while you open and close the bleeder valves on each wheel, starting with the furthest wheel from the master cylinder.
7. Test the System:
* Reconnect the battery.
* Start the engine. Listen for any unusual vacuum leaks.
* Carefully test the brakes. They should feel firm and responsive. If not, there is likely an issue. If necessary use a vacuum pump or gauge to test the booster.
* Drive the vehicle carefully for a short distance, testing the brakes frequently.
8. Reinstall Removed Components: Reinstall any components you removed to gain access to the brake booster.
Important Considerations:
* Vacuum Leak: A vacuum leak in the system is a serious problem that can lead to poor braking performance. Inspect all vacuum lines and connections carefully during reassembly.
* Master Cylinder: If the master cylinder is showing signs of wear or damage, consider replacing it at the same time.
* Professional Help: If you are uncomfortable with this repair, consult a qualified mechanic. Brake system failure is extremely dangerous.
This is a general guide. Always refer to a repair manual specific to your 1995 GMC Jimmy for detailed instructions, torque specifications, and diagrams. Failure to follow proper procedures can result in serious injury or death.
