What does the Heatline F04 fault code mean?

Your boiler has become too hot and has shut itself down for safety, likely because water is not moving through the system correctly.

How much does it cost to fix Heatline error code F04?

Typical repair cost for the Heatline F04 fault is £120-350 including labour.

Check that all radiator valves are fully open

High temperature safety limit (Overheat)

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Each noise points to a different fault.

Sludge build-up — needs flushing, not bleeding.

Work through these before the call-out.