Boiler displays E08, no heating or hot water, pump may not run

Safety first: Isolate power and allow the boiler to cool. Some pump components may still be hot.

• Check system pressure: Ensure pressure is at 1.0–1.5 bar. Very low pressure can cause pump errors.
• Bleed air from pump (engineer task): On some Sime pumps there is a bleed screw in the centre. Place a cloth underneath, loosen the screw slightly to release trapped air until water appears, then retighten.
• Check pump operation: With power restored and a heat demand present, touch the pump body. It should vibrate slightly. If it hums but does not turn, the impeller may be jammed.
• Clean system filter: If a magnetic or mesh filter is installed on the return to the boiler, isolate and clean it to restore flow.
• Replace pump (engineer task): If the pump is electrically open-circuit or seized, the engineer should replace the pump head or complete pump assembly with a compatible Sime-specified unit.