Subaru 2009 IMPREZA Service Manual page 1211

12.Engine Cooling System Trouble in General
A: INSPECTION
Trouble
a. Insufficient engine coolant
b. Loose timing belt
c. Oil on timing belt
d. Malfunction of thermostat
e. Malfunction of water pump
f. Clogged engine coolant passage
g. Improper ignition timing
h. Clogged or leaking radiator
Over-heating
i. Defective radiator fan
j. Improper engine oil in engine coolant
k. Air/fuel mixture ratio too lean
l. Excessive back pressure in exhaust system
m. Insufficient clearance between piston and cylinder Adjust or replace.
n. Slipping clutch
o. Dragging brake
p. Defective radiator fan
a. Ambient temperature extremely low
Over-cooling
b. Defective thermostat
a. Loosened or damaged connecting units on hoses
b. Leakage from water pump
c. Leakage from water pipe
Engine d. Leakage around cylinder head gasket
coolant leaks
e. Damaged or cracked cylinder head and cylinder
block
f. Damaged or cracked thermostat cover
g. Leakage from radiator
a. Timing belt problem
b. Defective radiator fan
Noise
c. Defective water pump bearing
d. Defective water pump mechanical seal
Engine Cooling System Trouble in General
Possible cause
CO(H4DOTC)-31
Corrective action
Replenish engine coolant, inspect for leakage, and repair
it if necessary.
Repair or replace timing belt tensioner.
Replace.
Replace.
Replace.
Clean.
Inspect and repair ignition control system. <Ref. to
EN(H4DOTC)(diag)-2, PROCEDURE, Basic Diagnostic
Procedure.>
Clean, repair or replace.
Replace.
Replace the engine coolant. If ineffective, check, repair or
replace engine components.
Inspect and repair the fuel injection system. <Ref. to
EN(H4DOTC)(diag)-2, PROCEDURE, Basic Diagnostic
Procedure.>
Clean or replace.
Repair or replace.
Adjust.
Inspect the radiator fan relay, engine coolant temperature
sensor or fan motor and replace them.
Partly cover radiator front area.
Replace.
Repair or replace.
Replace.
Repair or replace.
Retighten cylinder head bolts or replace cylinder head
gasket.
Repair or replace.
Repair or replace.
Repair or replace.
Replace.
Replace.
Replace water pump.
Replace water pump.
COOLING