This procedure replaces the brake booster on a 2012-2018 Jeep Wrangler with 3.6L V6 engine, which assists brake pedal effort using engine vacuum.

Warnings

Tools required

Parts

• Brake booster assembly × 1 — Use OEM specification
• Brake master cylinder to booster gasket/seal × 1 — Often included with booster
• Vacuum hose (if deteriorated) × 1 — Inspect during removal
• Thread locker (medium strength) × 1 — Loctite 243 or equivalent

Fluids

• Mopar DOT 4 Brake Fluid — 1 qt

Preparation

1. Park vehicle on level surface, apply parking brake, and place wheel chocks behind rear wheels
2. Disconnect negative battery terminal to prevent accidental airbag deployment while working near pedals
3. Remove driver's side floor mat and any pedal area trim panels for access
4. Extract as much brake fluid as possible from master cylinder reservoir using turkey baster or fluid extractor to minimize spillage
5. Allow engine to cool completely if recently driven
6. Gather all tools and parts before beginning, as work must be completed without long interruptions

Procedure

1. 1

   Access brake pedal assembly inside cabin
   Remove the driver's seat to improve access to the brake pedal mounting area. Locate the brake pedal pushrod connection to the brake booster inside the cabin, above the brake pedal arm. Use a flashlight to identify the pushrod clevis pin and retaining clip. This connection point is critical for reassembly alignment.
2. 2

   Disconnect brake pedal from booster pushrod
   Remove the retaining clip securing the clevis pin that connects the brake booster pushrod to the brake pedal arm. Slide out the clevis pin to disconnect the pedal from the booster. Note the orientation and position of any bushings or spacers for reassembly. The pedal will now move freely without resistance.
   ⚠Take photos of the clevis pin assembly before disassembly. Incorrect reassembly can cause pedal binding or failure.
3. 3

   Disconnect vacuum hose from booster
   Open the hood and locate the vacuum hose connection on the brake booster (front side, near firewall). The booster is a large circular component mounted to the firewall behind the master cylinder. Disconnect the vacuum supply hose from the booster check valve by releasing the clamp and pulling the hose off. Inspect the check valve and hose for damage or deterioration.
   ℹ️The check valve should be in the hose or booster inlet. Do not lose this component; it prevents vacuum loss when engine is off.
4. 4

   Disconnect brake lines from master cylinder
   Using a line wrench (NOT a standard wrench), carefully loosen the two brake line fittings at the master cylinder. Have a drain pan ready to catch fluid. Once loosened, immediately plug or cap the brake lines to prevent fluid loss and air entry. Do not allow brake fluid to contact painted surfaces. If the master cylinder will be separated from the booster, proceed; if removing as an assembly, skip to step 5.
   ⚠️Use only a line wrench to prevent rounding off brake line fittings. Damaged fittings can cause catastrophic brake fluid leaks.
   ⚠Brake fluid will drain rapidly once fittings are opened. Have plugs ready and work quickly.
   Torque spec

   Line Fittings23 Nm (17 lb-ft)
5. 5

   Remove master cylinder from booster (if separating)
   Remove the two nuts securing the master cylinder to the brake booster studs. Carefully pull the master cylinder straight off the booster, being careful not to damage the pushrod or seals. If removing the booster with master cylinder attached, skip this step and remove both as an assembly. Cap all master cylinder ports to prevent contamination.
   ℹ️Most technicians prefer to remove the master cylinder and booster together to avoid additional brake line disconnection.
   Torque spec

   Mounting Bolts31 Nm (23 lb-ft)
6. 6

   Remove brake booster mounting nuts from firewall
   From inside the vehicle cabin, locate the four nuts securing the brake booster to the firewall. These are accessed from behind the pedal assembly. Use a socket and extension to remove all four mounting nuts. Support the booster from the engine bay side to prevent it from falling when the last nut is removed.
   ⚠The booster and master cylinder assembly is heavy (20-30 lbs). Have an assistant support it from the engine bay or use a support stand.
7. 7

   Remove brake booster assembly
   From the engine bay, carefully pull the brake booster (with or without master cylinder attached) away from the firewall. Guide the mounting studs through the firewall holes. Maneuver the assembly out of the engine compartment, being careful not to damage brake lines or surrounding components. Set the assembly on a clean workbench.
8. 8

   Transfer master cylinder to new booster (if separated)
   If the master cylinder was removed separately, inspect the gasket/seal between the master cylinder and booster. Replace with new gasket. Align the master cylinder pushrod with the piston in the master cylinder and carefully slide the master cylinder onto the new booster studs. Install mounting nuts finger-tight initially. If the assembly was removed together, skip this step.
9. 9

   Install new brake booster to firewall
   From the engine bay, position the new brake booster assembly (with master cylinder) against the firewall, carefully aligning the four mounting studs with the firewall holes. Ensure the pushrod passes through the firewall opening and is aligned for pedal connection. From inside the cabin, thread all four mounting nuts onto the studs by hand, ensuring proper thread engagement.
   ⚠Do not force the booster into position. The pushrod must align freely through the firewall without binding.
10. 10

    Torque booster mounting nuts
    From inside the cabin, torque the four brake booster mounting nuts to 31.0 Nm (23.0 lb-ft) in a cross-pattern to ensure even seating against the firewall. Verify the booster is seated flush against the firewall with no gaps.
    ⚠Over-torquing can crack the booster housing. Under-torquing can allow vacuum leaks and booster failure.
    Torque spec

    Mounting Bolts31 Nm (23 lb-ft)
11. 11

    Reconnect brake pedal to booster pushrod
    From inside the cabin, align the brake booster pushrod clevis with the brake pedal arm. Install any bushings or spacers in the correct orientation as noted during disassembly. Insert the clevis pin through the pedal arm and pushrod clevis, then secure with the retaining clip. Verify the pin is fully seated and the clip is properly installed. Test pedal movement by hand to ensure smooth operation without binding.
    ⚠️The clevis pin MUST be secured with its retaining clip. Failure will cause complete pedal disconnection and brake failure.
12. 12

    Torque master cylinder to booster (if separated)
    If the master cylinder was installed separately in step 8, torque the two master cylinder mounting nuts to 31.0 Nm (23.0 lb-ft). If the assembly was removed and installed together, verify nuts are torqued to specification.
    Torque spec

    Mounting Bolts31 Nm (23 lb-ft)
13. 13

    Reconnect brake lines to master cylinder
    Remove plugs from brake lines and master cylinder ports. Thread brake line fittings into master cylinder ports by hand to ensure proper thread engagement and prevent cross-threading. Using a line wrench, torque both brake line fittings to 23.0 Nm (17.0 lb-ft). Do not over-torque as this can damage the fittings or master cylinder ports.
    ⚠️Cross-threaded or improperly torqued brake line fittings will leak, causing brake failure. Verify proper thread engagement before tightening.
    Torque spec

    Line Fittings23 Nm (17 lb-ft)
14. 14

    Reconnect vacuum hose to booster
    Install the vacuum check valve into the brake booster inlet if removed. Connect the vacuum supply hose to the check valve, ensuring it is fully seated. Secure with the hose clamp. Verify the connection is tight and properly positioned away from hot engine components.
    ℹ️The check valve has a directional flow. The side with the larger opening typically faces the booster.
15. 15

    Bleed brake system completely
    Fill the master cylinder reservoir with fresh Mopar DOT 4 brake fluid to the MAX line. Bleed the brake system using the proper sequence (typically: right rear, left rear, right front, left front) until all air is removed and only clear, bubble-free fluid emerges from each bleeder. Use a pressure bleeder or two-person manual bleeding method. Maintain reservoir level throughout bleeding process. Torque all bleeder screws to 16.0 Nm (12.0 lb-ft) when complete.
    ⚠️Incomplete bleeding will result in a spongy pedal and reduced braking ability. Continue bleeding until pedal is firm and no air bubbles are visible.
    ⚠Never reuse brake fluid. Always use fresh DOT 4 fluid from a sealed container.
    Torque spec

    Bleeder Screw16 Nm (12 lb-ft)

Reassembly

1. Reinstall driver's seat and any removed trim panels or floor mats
2. Reconnect negative battery terminal
3. Top off master cylinder reservoir to MAX line with fresh Mopar DOT 4 brake fluid
4. Clean any brake fluid residue from painted surfaces immediately with water

Verification

• With engine off, pump brake pedal several times. Pedal should be firm, not spongy. If spongy, re-bleed system
• Start engine. Pedal should drop slightly as vacuum assist activates. If pedal does not drop, check vacuum hose connection and check valve
• With engine running, apply firm brake pressure and hold for 30 seconds. Pedal should not sink. If it sinks, there is a leak or air in the system
• Check all brake line connections for leaks while assistant applies brake pressure
• Perform a low-speed test drive in a safe area to verify normal brake operation and pedal feel before returning to normal driving
• Verify no warning lights on instrument cluster related to brake system
• Check master cylinder fluid level after test drive and top off if needed
• Re-check all connections and torque specifications after first 50 miles of driving

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