my Ford F-150 13th Generation (2015-2020) loses coolant but no visible leaks

Solution

1. Preparation

• Gather tools and materials: OBD-II scanner, coolant, combustion leak tester, socket set, torque wrench, and new gaskets if necessary.
• Safety warning: Disconnect the battery before starting work on the engine, and allow the engine to cool.

2. Conduct Compression Test

• Remove the spark plugs using a socket set.
• Insert a compression tester into each cylinder, cranking the engine several times to get readings.
• Record the compression values for each cylinder; compare them to manufacturer specifications.

3. Address Head Gasket Failure (if applicable)

• If compression values are low, proceed with head gasket replacement.
  • Drain the coolant and remove the intake manifold.
  • Remove the cylinder head bolts in the correct sequence (refer to the service manual for the specific sequence and torque values).
  • Carefully lift the cylinder head off and replace the head gasket with a new one.
  • Clean the mating surfaces thoroughly to ensure a proper seal.

4. Reassemble Components

• Reinstall the cylinder head and tighten the bolts to the specified torque values in the correct sequence.
• Reattach the intake manifold and any other components removed during disassembly.
• Refill the coolant system with the correct type and mixture of coolant.

5. Final Checks

• Reconnect the battery and start the engine, checking for leaks.
• Use the OBD-II scanner to clear any diagnostic codes and monitor engine performance.