Mercedes-Benz GLC: M264 auxiliary electric coolant pump failure

The M264 2.0T engine uses an electric auxiliary coolant pump to circulate coolant through the turbocharger and engine after hot shutdown, preventing heat soak damage, and to support the main water pump during peak load. The electric pump uses brushless motor technology but the impeller and motor winding are prone to premature failure, particularly in vehicles that frequently cycle through hot-shutdown events such as urban stop-start driving. Failure is typically electronic: the pump motor windings fail causing the ECU to log a coolant pump fault and illuminate the engine warning light or overtemperature warning. In some cases the pump seizes, causing localised coolant flow restriction and triggering an overtemperature event that forces engine power reduction to protect head gasket integrity.

• Engine coolant temperature warning light or overtemperature message on cluster
• P0A9A or similar electric coolant pump fault codes stored
• Engine power reduction warning linked to overtemperature protection mode
• Coolant pump running audibly after hot shutdown then stopping prematurely
• In failed cases: pump completely silent during post-run cycle

1. 1

   Scan ECU for P0A9A, P2591, or manufacturer-specific electric water pump fault codes.

2. 2

   With XENTRY, perform electric coolant pump actuation test and verify flow audible at pump outlet.

3. 3

   Inspect pump connector for corrosion and fretting.

4. 4

   Check coolant for contamination that could block pump impeller.

5. 5

   Verify pump is genuine Mercedes-Benz part or quality OEM equivalent - aftermarket pumps have high repeat failure rates.

Parts involved: Water pump.

$650 to $1,600 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 vehicle ever displayed a coolant temperature warning or overtemperature message?”
• “Has the electric water pump been replaced at any point?”
• “Are there any stored or current fault codes relating to coolant or engine temperature?”
• “What is the coolant service history - has it been flushed at recommended intervals?”

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.