About this part
The 059121012B auxiliary water pump is the genuine OEM electric after-run coolant pump for Volkswagen Group V6 engines, listed here for Audi A6, A7, A8, A4, A5, Q5, Q7, VW Touareg and Phaeton applications.
What this pump does
The 059121012B is the electric auxiliary coolant pump (after-run pump) on the Volkswagen Group V6 engines — above all the 3.0 V6 TDI fitted across the Audi A6, A7, A8, Q5 and Q7, the VW Touareg and the Phaeton. It is a 12 V pump with a polymer impeller, driven independently of engine speed and switched by the engine control unit for three jobs. It keeps coolant moving after you switch off, so heat soaks out of the turbocharger and the cylinder head instead of sitting in the oil. It supports the heater, because at idle the mechanical pump turns slowly and the cabin on a V6 with a long heater circuit goes lukewarm without help. And it feeds the supplementary circuits — auxiliary heater, EGR and gearbox oil cooler loops — during warm-up.
Physically it is a short black cylindrical body with a machined white sealing collar, two plastic coolant stubs (supplied capped, as photographed), the two-pin electrical connector and the steel mounting bracket with its captive spring bolts. The stamping on the housing — VW and Audi rings, 059 121 012 B, DE BMH — is the only reliable identifier; two pumps of this shape can carry different internals.
OE / reference numbers
059121012B · 059 121 012 B, with the VW and Audi rings and the DE BMH casting mark stamped on the black housing, exactly as shown in the listing photographs. Same family: 059121012, 059121012A and 059121004J. Cross references quoted by aftermarket suppliers include Porsche 958 106 313 00 and 9A7 121 601 A. Because the 059 family shares a mounting pattern with several different flow rates, match the number stamped on your old pump — this is not the same pump as 1K0965561J (four-cylinder transverse cars) or 5N0965561A (four-cylinder TDI).
How the pump fails, and what you notice first
Stored fault code P2681. “Engine coolant auxiliary pump control circuit open” is the most common presentation: the ECU sends the duty signal and measures no current. On the V6 TDI it is often found as a stored code long before the driver notices anything.
Coolant crust at the collar. The sealing collar where the motor meets the pump housing is the weak point. A pink or white chalky deposit there means the shaft seal has started weeping — and on the V6 TDI the pump sits low enough that the drips are usually blown backwards and misread as a hose or radiator leak. Check the connector at the same time: coolant tracks up the harness and corrodes the pins, which is why a new pump sometimes does not fix the code.
Heater that goes cool at idle. Warm on the move, cool at the lights. On the A6 and A8 this is textbook auxiliary pump failure and gets misdiagnosed as a blocked heater core or a stuck thermostat surprisingly often.
Intermittent running. Worn brushes or a tight bearing: the pump works when cold and stops once hot. A pump that is intermittent is a pump that has failed — it is protecting the turbo after shutdown, and when it stops doing that the oil in the bearing housing cokes. Replace it rather than living with it.
Compatible vehicles
Fits vehicles built with the 3.0 V6 TDI (and the 2.7 V6 TDI where listed) and the V6 variants that use this pump. Model year, market and engine variant decide the final fitment — confirm against the table, the number on your old pump and your VIN.
| Make | Model | Years | Engine |
|---|---|---|---|
| Audi | A6 (4F2, 4F5, C6) | 2004 – 2011 | 2.7 / 3.0 V6 TDI |
| Audi | A6 (4G2, 4G5, C7) | 2011 – 2018 | 3.0 V6 TDI |
| Audi | A7 Sportback (4GA, 4GF) | 2010 – 2018 | 3.0 V6 TDI |
| Audi | A8 (4E2, 4E8, D3) | 2003 – 2010 | 3.0 V6 TDI |
| Audi | A8 (4H2, 4H8, D4) | 2010 – 2018 | 3.0 V6 TDI |
| Audi | A4 (8K2, 8K5, B8) | 2008 – 2016 | 3.0 TDI quattro |
| Audi | A5 (8T3, 8F7, 8TA) | 2008 – 2017 | 2.7 / 3.0 TDI |
| Audi | Q5 (8RB) | 2008 – 2017 | 3.0 TDI quattro |
| Audi | Q7 (4LB) | 2006 – 2015 | 3.0 V6 TDI |
| Volkswagen | Touareg (7P5, 7P6) | 2010 – 2018 | 3.0 V6 TDI |
| Volkswagen | Phaeton (3D) | 2007 – 2016 | 3.0 V6 TDI |
| Porsche | Cayenne (92A) | 2010 – 2018 | 3.0 V6 Diesel |
Fitting notes
Battery off before you open the circuit. The pump is switched on by the ECU even with the ignition off — it will run while you are unclipping hoses unless the battery is disconnected.
Flow direction matters. The pump circulates one way only. Match the arrow on the new housing to the old one, mark the hoses before you pull them, and push them on straight — the plastic stubs crack if they go on at an angle. Fit new clamps.
Check the plug, not just the pump. Before blaming the old pump, look at the connector pins for green corrosion and at the collar for coolant crust. If coolant has tracked up the harness, clean and dry the plug or the new pump will simply repeat the fault.
Bleed and clear codes. Refill, run the engine with the heater on full, and recheck the level when cold. Then clear the stored auxiliary pump faults and confirm they do not come back — a code that returns immediately usually means wiring or a fuse, not the pump.
Check the number before you order
The stamping on the housing is the only thing that identifies this pump reliably: VW and Audi rings, 059 121 012 B and the DE BMH mark. Shapes and photos are not enough — the 059 family shares a body across several flow ratings. Send us a photograph of the stamping on your old pump and your VIN and we will confirm the fitment before you order.
Shipping and packing
Orders leave within one to two working days of cleared payment. The coolant stubs stay capped and the bracket and spring bolts are padded so nothing loads on them in transit. Tracking is emailed when the parcel is handed to the carrier. Customs charges, where they apply, are the buyer’s responsibility.
Condition & warranty
Brand new, not remanufactured, twelve months warranty against manufacturing defects. A pump that has been run dry, fitted against the flow arrow or left with a corroded connector is outside the warranty — which is why the fitting notes above are worth two minutes of your time. If a unit fails in service, send us the fault description and photographs before returning anything.
Not sure this is the right pump?
Send us the VIN, the engine code from the data sticker, and a photograph of the number stamped on your old pump. We answer fitment questions before you order rather than after — a five minute check here saves a return and a second drain-down.
Wholesale
Tiered pricing for 1 pc, 5 pcs and 20 pcs is shown below. Workshops and resellers ordering several cooling-system parts together — thermostat, main water pump, hoses — should ask for a combined quote, we price mixed orders.
