How do I know if I need to change my water pump or my auxiliary water pump if my heater isn't as hot while idling?
Water Pump or Aux. water pump W123 replacement???
Dec 11, 2003
1 Replies
Feel the electric motor on the auxiliary pump while the engine is at idle to determine if the electric pump is running - or not. It can be unplugged quite easily to test it ON or OFF.
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