Subaru 2009 IMPREZA, Service Manual

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CO(H4SO)-28
Engine Cooling System Trouble in General
COOLING
11.Engine Cooling System Trouble in General
A: INSPECTION
Trouble Possible cause Corrective action
Over-heating
a. Insufficient engine coolant
Replenish engine coolant, inspect for leakage, and
repair it if necessary.
b. Loose timing belt Repair or replace timing belt tensioner.
c. Oil on timing belt Replace.
d. Malfunction of thermostat Replace.
e. Malfunction of water pump Replace.
f. Clogged engine coolant passage Clean.
g. Improper ignition timing
Inspect and repair ignition control system.
<Ref. to EN(H4SO)(diag)-2, Basic Diagnostic Procedure.>
h. Clogged or leaking radiator Clean, repair or replace.
i. Defective radiator fan Replace.
j. Improper engine oil in engine coolant
Replace the engine coolant. If ineffective, check, repair
or replace engine components.
k. Air/fuel mixture ratio too lean
Inspect and repair the fuel injection system. <Ref. to
EN(H4SO)(diag)-2, Basic Diagnostic Procedure.>
l. Excessive back pressure in exhaust system Clean or replace.
m. Insufficient clearance between piston and cylinder Adjust or replace.
n. Slipping clutch
Repair or replace.
o. Dragging brake Adjust.
p. Defective radiator fan
Inspect the radiator fan relay, engine coolant tempera-
ture sensor or fan motor assembly and replace them.
Over-cooling
a. Ambient temperature extremely low Partly cover radiator front area.
b. Defective thermostat Replace.
Engine coolant
leaks
a. Loosened or damaged connecting units on hoses Repair or replace.
b. Leakage from water pump Replace.
c. Leakage from water pipe Repair or replace.
d. Leakage around cylinder head gasket
Retighten cylinder head bolts or replace cylinder head
gasket.
e. Damaged or cracked cylinder head and cylinder block Repair or replace.
f. Damaged or cracked thermostat cover Repair or replace.
g. Leakage from radiator Repair or replace.
Noise
a. Timing belt problem Replace.
b. Defective radiator fan Replace.
c. Defective water pump bearing Replace water pump.
d. Defective water pump mechanical seal Replace water pump.