BMW 3 Series: Electric water pump (EWP) failure causing overtemp

The N52B25/N52B30 engine replaces the conventional belt-driven water pump with an electric unit controlled by the DME. The pump motor and impeller are a known failure point, typically between 80,000 and 130,000 km. Unlike a belt-driven failure, there is no gradual warning — the pump can fail suddenly at speed. When the pump stops, coolant flow ceases immediately and the engine can reach critical temperature within four to six minutes at highway load. The dashboard warning 'Engine Coolant — Stop Safely' should be treated as an immediate pull-over event. BMW extended the warranty on this component in several markets following a pattern of field failures. Replacement should include the auxiliary coolant pump and the electronic thermostat in the same service event to avoid a repeat job.

• Yellow 'Engine Coolant' overtemperature warning on iDrive
• Rapid temperature gauge climb with no prior warning
• Engine fan running at full speed at low vehicle speeds
• Loss of cabin heater output with engine up to temperature
• DME fault code 4822 (electric coolant pump) or 480E (thermostat)

With engine fully warmed and stationary, check that the coolant temperature stabilises around the midpoint on the gauge. Check for stored fault codes relating to the coolant pump or thermostat. Inspect coolant expansion tank for brown or rusty staining indicating a previously overheated episode. If a workshop inspection is possible: Connect a BMW ISTA or equivalent scan tool and command the electric water pump to full speed via the actuator test — pump should audibly increase flow.

Parts involved: Water pump.

$950 to $1,900 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

• “Has the electric water pump and thermostat been replaced? At what mileage?”
• “Has the car ever triggered an overtemperature warning or been driven with the temperature gauge in the red?”
• “When was the coolant last changed and what coolant specification was used?”

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.