why is my BMW 5 Series F10/F11 (2010-2017) losing coolant but no visible leaks

Solution

1. Preparation

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

2. Perform a Pressure Test

• Tools Required: Cooling system pressure tester
• Steps:
  1. Remove the coolant reservoir cap.
  2. Attach the pressure tester to the coolant expansion tank.
  3. Pump the tester to 15-20 psi and monitor for pressure drop.
  4. Inspect the engine bay and undercarriage for any signs of coolant leakage under pressure.

3. Inspect the Water Pump

• Tools Required: Socket set, torque wrench
• Steps:
  1. If leaks are detected, remove the accessory drive belt.
  2. Unbolt the water pump from the engine block.
  3. Inspect the water pump for signs of leakage or wear.
  4. Replace the water pump if any issues are found, ensuring to torque bolts to manufacturer specifications.

4. Check and Replace Head Gasket (if necessary)

• Tools Required: Socket set, torque wrench, gasket scraper
• Steps:
  1. If the compression test indicates a blown head gasket, remove the engine head by unbolting it carefully.
  2. Clean the mating surfaces thoroughly to remove old gasket material.
  3. Install a new head gasket and reassemble the engine, torque bolts to manufacturer specifications.
  4. Refill the coolant and bleed the system of air.