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5.9 Purpose, Troubleshooting, Dismounting, & Replacement of
the Pump
The electric motor and the pump
(Fig. 12) are used to circulate coolant
across the vehicle engine/cabin heat-
ing systems.
The pump may fail to operate for the
following reasons:
• Poor coolant quality (frozen
coolant)
• Foreign particles inside the
liquid circuit
• Short or open circuit in the
electric wiring
• Wear on the working parts of
the pump.
If the coolant is frozen (has turned
into a snow-like mass) inside the
pump, the pump may continue to
operate but will not be able to circu-
late any coolant. Unfreeze the pump
and replace the coolant with that of
better quality.
Where there are foreign particles
(such as ne chippings or sawdust)
inside the liquid circuit, they may
obstruct pump operation. A clear
symptom of a contaminated pump
is poor circulation of the coolant.
To clean the pump, partially disassem-
ble it in the following order:
• Remove the pump from
the vehicle
• Remove the four screws and
remove the cover
• Clean the cover and the spinner
of foreign particles
• Reinstall the cover and check the
pump operation
If the pump does not turn on, check
the wiring.
If the wiring is not visibly damaged,
connect an electric source at the
pump operating voltage directly to
the pump terminals for a short
period. If the pump starts, it is fault-
free. Check the wiring with
a multimeter.
Fig. 12. Electric motor with a pump
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