how to diagnose my BMW 3 Series E90/E91 (2005-2012) overheating problem

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the engine is cool before starting work.
• Disconnect the negative battery terminal for safety.

2. Inspect and Replace Coolant

• Sub-steps:
  1. Remove the coolant reservoir cap slowly to relieve any pressure.
  2. Drain the coolant from the radiator using a drain pan.
  3. Flush the cooling system with clean water to remove debris.
  4. Refill the system with the appropriate type and mixture of coolant (BMW-approved coolant).
• Tools Required: Drain pan, funnel.

3. Replace Thermostat (if faulty)

• Sub-steps:
  1. Remove the thermostat housing by unscrewing the bolts (torque specifications: 10 Nm).
  2. Take out the old thermostat and inspect the rubber gasket for damage.
  3. Install the new thermostat, ensuring it is oriented correctly.
  4. Reattach the thermostat housing and torque it to specifications.
• Tools Required: Socket set, torque wrench.

4. Replace Water Pump (if malfunctioning)

• Sub-steps:
  1. Disconnect the serpentine belt from the water pump.
  2. Remove any components obstructing access to the water pump (e.g., hoses).
  3. Unscrew the water pump bolts and remove the old pump.
  4. Clean the mounting surface and install the new water pump with a new gasket.
  5. Reassemble everything in reverse order, ensuring all components are secure.
• Tools Required: Socket set, torque wrench.

5. Test Radiator Fan

• Sub-steps:
  1. Reconnect the battery and start the engine.
  2. Allow the engine to reach normal operating temperature and observe if the radiator fan activates.
  3. If the fan does not operate, check the fan relay and wiring.
  4. Replace the fan if it is defective.
• Tools Required: Multimeter (if testing electrical components).