Coolant pump (V50)

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The coolant pump V50 is electrically powered and is operated when the ignition is switched on, its function is to continue circulating water around the engine/heater matrix when the engine is switched off, so that the heater output does not drop-off. Not only this, it ensures that there is no localized overheating in the engine block (or elsewhere) or large temperature deviations in the coolant system when the engine switches off in Ecomatic operation by ensuring the coolant is still circulated around, therefore, it is sensible to fix this if yours is non-operational not only for comfort but for long-term engine and cooling system reliability.

The 2-pin connector as well as connection pins are notorious for corrosion on this water pump, disconnect the connector and spray with electrical contact cleaner.

This pump can be replaced without having to remove anything other than the pump itself, the rubber mountings can also be installed correctly into the clutch positioner console bracket from underneath the car using angled and straight pin-nose pliers if they have popped out, it is not necessary to remove the clutch positioner console bracket to re-install them correctly.

Original part number: 251 965 561 A / 251965561A Replacement part number: 251 965 561 B / 251965561B (slightly different pump)

The pump is made by Bosch and can be sourced directly from them or relevant suppliers, which may cost less than the main dealer price.

In the UK, sell this pump for an incredibly low price.

Testing procedure

Test 1

Turn ignition on, but do not start engine, listen to pump and squeeze pipes leading into it, if no noise can be heard and no vibrations felt, it has probably failed, go to test 2.

Test 2

  1. Engine is warmed up
  2. Ecomatic mode switched on
  3. Turn temperature dial to hot
  4. Switch fan speed to 2
  5. Switch vent direction to face
  6. Allow engine to switch off via Ecomatic operation.
  7. If heat output starts to drop off in 30 seconds or less with engine off, restart the engine, if heat comes back, then the electric coolant pump has almost definitely failed.