Oil Separator/PCV

Replace the oil separator/PCV (Positive Crankcase Ventilation) system on a 2008 Dodge Viper 8.4L V10 to restore proper crankcase pressure management and prevent oil consumption issues.

Warnings

Tools required

Parts

• Oil separator assembly × 1 — Mopar 4891558AC or equivalent
• Oil separator mounting grommet/seal × 1 — Use OEM specification
• PCV hose clamps (if damaged) × 2 — Use OEM specification

Preparation

1. Ensure the engine is cold to the touch
2. Park vehicle on level ground and engage parking brake
3. Open the hood and secure with prop rod
4. Disconnect the negative battery cable to prevent accidental starter engagement while working near the intake area
5. Inspect the oil separator location on the passenger side of the engine between the valve cover and intake manifold
6. Place shop towels around the work area to catch any oil drips

Procedure

1. 1

   Remove engine cover (if equipped)
   If your Viper is equipped with an engine dress cover, remove the fasteners securing it. Typical configuration uses plastic push-pins or quarter-turn fasteners at multiple points. Lift the cover away to expose the intake manifold and valve covers.
2. 2

   Locate and inspect the oil separator assembly
   The oil separator/PCV component location on the 8.4L V10 must be confirmed against the factory service manual. Trace both hoses to understand the routing before removal.
3. 3

   Disconnect PCV hose from intake manifold
   Locate the PCV hose connection at the intake manifold (verify exact location against the factory service manual for the 8.4L V10). Use a flat blade screwdriver or pick tool to carefully release the hose clamp. Twist the hose gently while pulling to break any seal created by oil residue, then disconnect the hose from the intake manifold fitting. Position the catch pan below to collect any oil drips.
4. 4

   Disconnect breather hose from valve cover
   At the valve cover end, locate the breather hose connection. Release the clamp using a flat blade screwdriver or by compressing spring-type clamp ears with pliers. Twist and pull the hose from the valve cover nipple. Some oil vapor condensate may drain from this connection.
5. 5

   Remove oil separator mounting fasteners
   The oil separator mounting fastener count and head size must be verified against the factory service manual before removal. Remove the mounting fasteners and retain them for reinstallation. The separator may also use a rubber grommet mount point.
6. 6

   Remove oil separator assembly
   Carefully lift the oil separator assembly away from its mounting position. The unit will still have both hoses attached. Tilt it to drain any residual oil into your catch pan. Inspect the mounting grommet or seal for deterioration; replace if cracked or compressed.
7. 7

   Remove hoses from old separator (if reusing hoses)
   If the PCV hoses are in good condition and not included with the replacement separator, remove them from the old unit by releasing any remaining clamps. Inspect hoses for cracks, oil saturation, or collapsed sections. Replace hoses if they show deterioration or have lost flexibility.
8. 8

   Prepare new oil separator for installation
   Unpack the new oil separator assembly. If hoses are not pre-attached, install the PCV hoses onto the separator's inlet and outlet ports, ensuring proper orientation. The shorter hose typically connects to the valve cover breather, while the longer hose routes to the intake manifold. Install new hose clamps loosely at this stage.
9. 9

   Install new mounting grommet/seal
   If the separator uses a rubber mounting grommet, install the new grommet into the valve cover or mounting bracket location. Ensure it seats fully and is properly oriented to receive the separator body.
10. 10

    Position and mount new oil separator
    Position the new oil separator assembly into its mounting location, inserting it into the rubber grommet if equipped. Align the mounting holes and install the 2 mounting bolts. Tighten fasteners securely but do not overtighten, as this can compress the mounting grommet excessively.
11. 11

    Connect breather hose to valve cover
    Route the breather hose to the valve cover nipple. Push the hose firmly onto the fitting until fully seated. Position the hose clamp approximately 1/4 inch from the end of the hose and tighten securely. Verify the connection is firm by attempting to twist the hose.
12. 12

    Connect PCV hose to intake manifold
    Route the PCV hose from the separator to the intake manifold PCV inlet fitting. Ensure the hose follows the original routing path without kinks or sharp bends. Push the hose fully onto the intake manifold fitting, position the clamp, and tighten securely.
13. 13

    Verify all connections and routing
    Perform a visual inspection of both hose connections, ensuring clamps are tight and hoses are fully seated. Check that hoses do not contact hot exhaust components, sharp edges, or moving parts. Verify the oil separator is securely mounted and does not move when gently manipulated.
14. 14

    Reinstall engine cover and reconnect battery
    If an engine dress cover was removed, reinstall it with all fasteners. Reconnect the negative battery cable. Remove shop towels and close the hood.

Reassembly

1. Ensure all hose clamps are positioned correctly and tightened to prevent vacuum leaks
2. Verify no tools or shop towels have been left in the engine bay
3. Double-check that the oil separator mounting is secure and the unit does not vibrate when the engine runs

Verification

• Start the engine and allow it to idle for 2-3 minutes
• Listen for any hissing sounds that would indicate a vacuum leak at the PCV hose connections
• Check for oil leaks around the separator mounting points and hose connections
• Monitor engine idle quality; rough idle or fluctuating RPM may indicate improper PCV system function
• Rev the engine slightly and verify the PCV system is functioning by feeling for suction at the oil filler cap (should have slight vacuum pull when cap is loosened at idle)
• Road test the vehicle and verify no check engine light illuminates related to fuel trim or intake leaks

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