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How to fix coolant leak issue in BMW E46 318i (N42B18)?

Posted: Tue Oct 01, 2024 11:41 am
by spinecki
How to fix coolant leak issue in BMW E46 318i (N42B18)?

Common leak sources:
  • Expansion tank
  • Radiator
  • Water pump
  • Thermostat housing
  • Hoses and connections
Diagnostic steps:
  • Visual inspection of all coolant components
  • Pressure test the cooling system
  • Use UV dye to locate small leaks
Repair procedures:
  • Expansion tank replacement:
    - Drain coolant
    - Remove hoses and electrical connections
    - Replace tank (BMW part number: 17117573781)
  • Radiator replacement:
    - Remove fan shroud and electric fan
    - Disconnect hoses and remove radiator
    - Install new radiator and refill system
  • Water pump replacement:
    - Remove serpentine belt
    - Remove water pump bolts and replace pump
Note: Always use BMW-approved coolant and properly bleed the cooling system after repairs.