Cooling System Inspection - BMW 5251 Service Manual

170-8
I
Radiator
and
Cooling
System
Common cooling system faults can be grouped into one of 4
categories:
Cooling system lealts
Poor coolant circulation
Radiator cooling fan faults
Electrical/electronic faults
Cooling system inspection
-
Check that coolant pump drive belt tensioner is functioning
properly and that belt tension is correct. Belt tensioner sys-
tems for the different models are shown in
020
Maintenance.
-
Check condition of coolant pump drive belt.
-
Checlc coolant hoses for cracks or softness. Checlc clamps
for looseness. Check coolant level and check for evidence of
coolant lealts from engine.
-
Check that radiator fins are not blocked with dirt or debris.
Clean radiator using low-pressure water or compressed air.
Blow outward, from engine side out.
-
To check coolant pump:
Remove mechanical cooling fan. See Mechanical (vis.
cous clutch) cooling fan, removing and installing.
Remove drive belt from coolant pump pulley. See
020
Maintenance.
Firmly grasp opposite sides of pulley and check for play in
all directions.
Spin pulley and check that shaft runs smoothly without
play.
NOTE-
The coolant provides lubrication for the pump shaft, so an oc-
casional drop of coolant lealing from the pump is acceptable.
If coolant drips steadily from the vent hole, replace the pump.
-
At normal engine operating temperature, cooling system is
pressurized. This raises boiling point of coolant. Leaks may
prevent system from becoming pressurized. If visual evi-
dence is inconclusive, pressure test cooling system as de-
scribed later to help pinpoint hard-to-find leaks.
-
If cooling system is full of coolant and holds pressure:
-
Use an appropriate scan tool to interrogate engine control
module (ECM) for radiator fan or DME control circuit faults.
Checlc for loose or worn drive belt.
0
Test for failed thermostat or coolant pump impeller. Some
pumps may be fitted with plastic impellers.