HOW TO - Remove and Replace Coolant Expansion Tank on BMW 335i

Introduction

This tutorial provides a step-by-step guide on how to remove and replace the coolant expansion tank on a BMW 335i, specifically focusing on the E92 model. The coolant expansion tank is crucial for maintaining the engine's cooling system by managing coolant levels and preventing overheating. Proper maintenance and replacement of this component can help avoid costly engine damage.

Step 1: Gather Necessary Tools and Materials

Before starting the replacement process, ensure you have the following tools and materials ready:

• Flathead screwdriver
• Pliers
• Ratchet and socket set (typically 10mm)
• New coolant expansion tank
• BMW-approved coolant
• Distilled water
• Clean cloths or rags
• Safety goggles and gloves

Step 2: Prepare the Vehicle

• Ensure Safety: Park the vehicle on a level surface and engage the parking brake.
• Cool Down the Engine: Wait for the engine to cool down completely to avoid burns from hot coolant.
• Open the Hood: Secure the hood with a prop rod to keep it open.

Step 3: Remove the Old Coolant Expansion Tank

• Locate the Expansion Tank: The coolant expansion tank is usually situated near the front of the engine bay.
• Disconnect the Hoses:
  • Use pliers to loosen the clamps on the hoses connected to the expansion tank.
  • Carefully pull off the hoses and set them aside.
• Remove the Mounting Bolts:
  • Use a ratchet and socket to remove the bolts securing the expansion tank.
  • Keep the bolts in a safe place for reinstallation.
• Take Out the Expansion Tank: Gently pull the tank out of its mounting position.

Step 4: Install the New Coolant Expansion Tank

• Position the New Tank: Place the new expansion tank into the same position as the old one.
• Secure with Bolts:
  • Reinstall the mounting bolts and tighten them securely.
• Reconnect the Hoses:
  • Push the hoses back onto the corresponding ports on the new tank.
  • Ensure the clamps are tightened securely to prevent leaks.

Step 5: Refill the Coolant System

• Prepare the Coolant Mixture: Mix BMW-approved coolant with distilled water in a 50/50 ratio.
• Pour the Coolant: Carefully pour the coolant mixture into the expansion tank until it reaches the recommended level.
• Check for Leaks: Start the engine and let it run for a few minutes while checking for any leaks around the expansion tank.

Step 6: Final Checks

• Monitor the Coolant Level: After the engine has cooled down, check the coolant level again and top off if necessary.
• Dispose of Old Coolant: Properly dispose of any old coolant and any materials used during the replacement process.

Conclusion

Replacing the coolant expansion tank on your BMW 335i is a straightforward task that can enhance your vehicle's performance and longevity. Regular maintenance of the cooling system is essential to prevent overheating and ensure your engine runs smoothly. If you encounter any issues during the replacement process, consider consulting a professional mechanic for assistance.