my BMW 3 Series F30/F31 (2012-2019) has a coolant leak, where should I look?

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery to prevent any electrical issues during the repair.

2. Inspect and Replace Leaking Components

2.1 Coolant Reservoir

• Remove the coolant reservoir cap and inspect for cracks.
• If damaged, remove the reservoir by disconnecting the hoses and mounting points.
• Install the new coolant reservoir, reconnect hoses, and fill with coolant.

2.2 Hoses

• Inspect all coolant hoses for wear, cracking, or leakage.
• Cut and remove damaged hoses using a hose cutter.
• Install new hoses, ensuring they are securely fastened with clamps.

2.3 Radiator

• Check the radiator for leaks or damage; if found, it may need to be replaced.
• Remove the upper and lower radiator hoses and disconnect the transmission cooler lines if applicable.
• Unbolt the radiator from its mounting points and replace it with a new unit.
• Reconnect all hoses and refill coolant.

2.4 Water Pump

• Locate the water pump and inspect for leaks around the gasket.
• If leaking, remove the serpentine belt and unbolt the water pump.
• Replace with a new water pump and ensure proper gasket sealing.
• Reinstall the serpentine belt.

2.5 Thermostat Housing

• Remove any components obstructing access to the thermostat housing.
• Unbolt the housing and check for leaks; replace if necessary.
• Clean the mating surfaces and install a new gasket before reassembling.

3. Refilling and Bleeding the Cooling System

• Fill the coolant reservoir with the appropriate coolant mixture.
• Start the engine with the radiator cap off to allow air to escape.
• Run the engine until it reaches operating temperature, topping up coolant as necessary.
• Replace the radiator cap and check for leaks after the system is pressurized.