how to fix a coolant leak in my BMW 3 Series E90/E91?

Solution

1. Preparation

• Gather all necessary tools and parts.
• Park the vehicle on a level surface and ensure the engine is cool.
• Disconnect the battery to avoid any electrical issues.

2. Identify and Replace Leaking Hoses

• Tools Required: Hose clamp pliers, screwdriver, coolant catch pan.
• Use hose clamp pliers to remove the clamps from the leaking hose.
• Disconnect the hose from the fittings, allowing any remaining coolant to drain into the catch pan.
• Replace the damaged hose with a new one, ensuring it matches the specifications of the original.
• Reattach the clamps securely.

3. Repair or Replace the Radiator

• Tools Required: Socket set, coolant catch pan, new radiator (if necessary).
• Disconnect the hoses from the radiator and let the coolant drain into the catch pan.
• Remove the mounting bolts securing the radiator to the vehicle.
• If the radiator is damaged, replace it with a new unit.
• Reinstall the radiator and reconnect the hoses.

4. Replace the Water Pump (if applicable)

• Tools Required: Socket set, wrench set, new water pump, gasket or sealant.
• Drain the coolant as previously described.
• Remove the drive belt from the water pump.
• Unbolt the water pump from its housing and remove it.
• Clean the mounting surface and install the new water pump with a new gasket or sealant.
• Reattach the drive belt.

5. Refill Coolant and Bleed the System

• Tools Required: Funnel, coolant (specific to BMW specifications).
• Refill the cooling system with the appropriate coolant mixture.
• Start the engine and allow it to reach operating temperature, then turn the heater on to maximum.
• Open the bleed screw (if equipped) on the cooling system to release trapped air until coolant flows steadily.
• Close the bleed screw and check for leaks.