Remove and replace the brake booster assembly on a 2014 Ram 2500 with 6.7L Cummins diesel engine, including master cylinder removal and brake system bleeding.

Warnings

Tools required

Parts

• Brake booster assembly × 1 — Use OEM specification
• Brake booster gasket/seal × 1 — Usually included with booster
• Master cylinder gasket × 1 — If not reusing existing
• Brake fluid × 1 — Mopar DOT 4

Fluids

• Mopar DOT 4 Brake Fluid — 1 qt

Preparation

1. Park vehicle on level ground and set parking brake. Place wheel chocks behind rear wheels.
2. Disconnect negative battery cable and isolate to prevent airbag deployment during work near steering column.
3. Remove driver side floor mat and any carpet trim panels for access to pedal assembly.
4. Open hood and locate brake master cylinder and booster assembly on driver side firewall.
5. Using turkey baster or fluid extractor, remove as much brake fluid as possible from master cylinder reservoir to minimize spillage.
6. Place protective covers over fender and inner fender area to protect from brake fluid damage.
7. Prepare clean workspace and ensure all replacement parts are available before beginning disassembly.

Procedure

1. 1

   Disconnect brake lines from master cylinder
   Working in engine compartment, identify the two brake lines connected to master cylinder. Using proper brake line wrenches (not standard wrenches which will round fittings), carefully loosen and remove both brake line fittings from master cylinder ports. Immediately cap or plug the lines and ports to prevent fluid loss and contamination. Place a drain pan or absorbent material below work area to catch residual fluid.
   ⚠Use only brake line wrenches to prevent rounding off brass fittings. Rounded fittings will require line replacement.
2. 2

   Remove master cylinder from brake booster
   Locate the two nuts securing master cylinder to brake booster studs. These are accessible from engine compartment. Remove both nuts using appropriate socket. Carefully pull master cylinder straight off booster studs and move aside. Support master cylinder to prevent stress on any remaining connections. If equipped with fluid level sensor, disconnect electrical connector.
   Torque spec

   Master Cylinder Nuts25 Nm (18 lb-ft)
3. 3

   Disconnect vacuum line from brake booster
   Locate vacuum line connection at brake booster check valve (typically on front or side of booster). On 6.7L Cummins diesel, this vacuum line runs from engine-mounted vacuum pump. Release clamp and carefully remove vacuum hose from booster check valve. Inspect check valve for damage; if stuck or damaged, remove and replace. Plug vacuum line to prevent debris entry.
4. 4

   Access brake pedal pushrod connection from interior
   Move to vehicle interior. Using flashlight, locate the brake pedal pushrod connection point above brake pedal. The pushrod connects to brake pedal arm with a clevis pin and retaining clip. This area is very tight and requires working upside-down under dash. Note the orientation of all components for reassembly.
   ℹ️This is the most physically difficult part of the job due to tight working space. Consider using a mirror to see connection point clearly.
5. 5

   Disconnect pushrod from brake pedal
   Remove retaining clip securing clevis pin at brake pedal arm. Remove clevis pin and disconnect pushrod from brake pedal. The pushrod may have a locking nut at the clevis; if adjustable, note exact position before loosening. Keep all hardware organized as reassembly must be exact.
   ⚠Do not alter pushrod length adjustment during removal. Mark or measure position if any adjustment is present.
   Torque spec

   Brake Pedal Pushrod Lock15 Nm (11 lb-ft)
6. 6

   Remove brake booster mounting nuts from firewall
   From interior side, locate four nuts securing brake booster to firewall. These nuts are on studs protruding through firewall from engine compartment side. Remove all four nuts using appropriate socket. Support booster from engine compartment side to prevent it from falling when last nut is removed.
   Torque spec

   Brake Booster Nuts25 Nm (18 lb-ft)
7. 7

   Remove brake booster assembly
   Working from engine compartment, carefully pull brake booster assembly away from firewall. Guide pushrod through firewall opening as booster is removed. The booster is heavy and awkward; use caution to avoid dropping. Remove and discard old gasket/seal from firewall mounting surface. Clean firewall mounting surface thoroughly, removing all old gasket material and debris.
8. 8

   Prepare and install new brake booster
   Inspect new brake booster for correct part number and included components. Check that check valve is installed and vacuum port is oriented correctly for hose routing. Install new gasket/seal on firewall mounting surface or on booster as specified. If pushrod length is adjustable on new booster, verify it matches old unit measurement. From engine compartment, align booster with firewall studs and carefully push into position, guiding pushrod through firewall opening.
   ⚠Verify pushrod protrusion matches original booster. Incorrect pushrod length will cause brake drag or excessive pedal travel.
9. 9

   Install booster mounting nuts and reconnect pushrod
   From interior, install all four brake booster mounting nuts finger-tight first, then torque in a cross pattern to specified value. Connect pushrod clevis to brake pedal arm, install clevis pin and secure with retaining clip. If pushrod has adjustable length with lock nut, verify adjustment matches original and torque lock nut to specification. Verify brake pedal returns fully and has normal free play.
   ⚠Tighten mounting nuts in cross pattern to ensure even seating against firewall.
   Torque spec

   Brake Booster Nuts25 Nm (18 lb-ft)

   Brake Pedal Pushrod Lock15 Nm (11 lb-ft)
10. 10

    Reconnect vacuum line and install master cylinder
    Connect vacuum hose to brake booster check valve and secure with clamp. Verify check valve orientation (arrow should point toward booster). Install new master cylinder gasket if applicable. Position master cylinder onto booster studs, ensuring it seats fully against booster. Install master cylinder mounting nuts and torque to specification.
    Torque spec

    Master Cylinder Nuts25 Nm (18 lb-ft)
11. 11

    Reconnect brake lines to master cylinder
    Remove plugs/caps from brake lines and master cylinder ports. Thread brake line fittings into master cylinder ports by hand to ensure proper thread engagement. Once both fittings are hand-tight, use brake line wrenches to tighten securely. Do not overtighten as brass fittings can strip. Reconnect fluid level sensor electrical connector if equipped.
    ⚠Cross-threading brass brake fittings will require master cylinder or line replacement. Thread carefully by hand first.
12. 12

    Fill and bleed brake system
    Fill master cylinder reservoir with new Mopar DOT 4 brake fluid to MAX line. Bleed brake system starting at wheel farthest from master cylinder (right rear), then left rear, right front, left front. At each wheel, attach bleeder hose to bleeder screw, submerge other end in container with clean brake fluid. Have assistant pump brake pedal several times and hold pressure while you open bleeder screw briefly to release fluid and air. Close bleeder screw before pedal reaches floor. Repeat until no air bubbles appear. Torque bleeder screws to specification. Maintain reservoir fluid level throughout bleeding process.
    ⚠️Bleeding must be thorough and complete. Air in brake lines causes spongy pedal and reduced braking force. If pedal feel is not firm after bleeding, repeat process or use scan tool for ABS bleeding.
    ⚠Never let master cylinder run dry during bleeding as this introduces air into system.
    Torque spec

    Bleeder Screw18 Nm (14 lb-ft)
13. 13

    Verify vacuum pump operation and booster function
    Reconnect battery negative cable. Start engine and verify vacuum pump operation (should hear pump running on diesel). With engine running, press brake pedal and verify power assist is present (pedal should require less force than with engine off). Turn engine off and pump brake pedal several times to deplete vacuum reserve. On final pump, pedal should be firm. Then start engine while maintaining light pressure on pedal; pedal should sink slightly as booster vacuum builds, confirming proper booster operation.
    ⚠️If brake pedal does not exhibit power assist or feels abnormal, DO NOT drive vehicle. Recheck all connections and bleeding procedure.

Reassembly

1. Verify all brake line connections are tight and show no signs of leakage.
2. Check master cylinder fluid level and top off to MAX line with Mopar DOT 4 brake fluid.
3. Reinstall driver side floor mat and any interior trim panels that were removed.
4. Remove fender protection and clean any brake fluid residue with water immediately.
5. Verify brake pedal height and free play are within normal range and pedal returns fully to rest position.

Verification

• With engine running, press brake pedal firmly and hold for 30 seconds. Pedal should remain firm with no sinking, indicating no internal or external leaks.
• Perform brake booster test: With engine off, pump brake pedal until firm, then start engine while holding light pedal pressure. Pedal should sink slightly and remain easy to press, confirming booster vacuum operation.
• Test drive vehicle in safe area at low speed. Brake pedal should feel firm and responsive with no sponginess. Braking should be straight and even.
• After test drive, inspect all brake line connections and master cylinder for any signs of fluid leakage.
• Check master cylinder fluid level again after test drive; top off if needed.
• CRITICAL: If brake pedal feels soft, spongy, or travels too far, or if braking performance is not normal, DO NOT drive vehicle on public roads. Repeat bleeding procedure or seek professional diagnosis. This is a safety-critical system.

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