2 min read


One of the main faults of the N55 Engine is the Oil Filter Housing Gasket (OFHG), and when it fails things seem grim. If it fails, oil can get into the coolant, making it seem like the engine is compromised and a bill of tens of thousands coming your way... Fret not, this blog is to catch the symptoms, how to test, and what to look out for when fixing this system. By understanding and maintaining your N55's OFHG, you can manage and prevent potential issues effectively.


  • Oil in Coolant ("milkshake" appearance): This issue arises due to the higher pressure in the oil passage adjacent to a coolant line within the Oil Filter Housing (OFH), allowing oil to mix into the coolant. However, this does not typically result in coolant entering the oil system.

  • Engine Overheating: Contaminated coolant can impair its flow and heat transfer capabilities, leading to overheating. It is crucial to stop driving and tow your vehicle to a service location to prevent further damage.

  • No Heat from Climate Control: Oil contamination can disrupt the function of the heater core valve, preventing coolant from reaching the heating unit and thus disabling the heating system.


Replace OFHG: This is the first step to stop further oil leakage into the coolant. 

  • Flush the Cooling System: Perform a thorough flush to remove any oil residue.
  • Inspect and Possibly Replace Additional Cooling System Components:

    • Thermostat (T-stat)
      • Water Pump
        • Heater Core
          • Heater Core Valve
          • Heater Core Hose
            • Oil Filter

               IMPORTANT NOTE

            • Priming the Oil Pump: After replacing the oil pan or OFHG, it's crucial to prime the oil pump to prevent dry running which can damage the engine. This can be done by pulling the fuses for the high and low pressure fuel pumps, typically found in the fuse box (refer to the fuse box lid for specific numbers).

          CONCLUSION After addressing these issues, continuous monitoring of the OFHG is advised. Similar to the water pump, the OFHG is prone to recurring issues and should be treated as a regular maintenance item. Vigilance and preventive maintenance can significantly extend the life of your N55 engine and reduce the likelihood of severe engine problems.

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