Cooling System Pressure Test - BMW 1999-2005 M3 Service Manual

Radiator and Cooling System
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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 occasional drop of
coolant leaking from the pump is
acceptable. If coolant drips steadily
from the vent hole, the pump should be
replaced.
The cooling system becomes
pressurized at normal operating
temperature, which raises the boiling
point of the coolant. Leaks may prevent
the system from becoming pressurized,
allowing the coolant to boil at a lower
temperature. If visual evidence is
inconclusive, a cooling system
pressure test can help to pinpoint
hard-to-find leaks.
If the cooling system is full of coolant
and holds pressure, the next most
probable causes of overheating are:
Faulty radiator fan or DME control
circuit. Use an appropriate scan
tool to interrogate the DME control
module for faults.
Loose or worn drive belt.
Failed thermostat or coolant pump
impeller. Some pumps may be
fitted with plastic impellers.
Clogged/plugged radiator or
coolant passages.

Cooling system pressure test

2/25/2009 9:57 PM