Page 2758 of 3051

+Replace the radiator cap if abnormalities are found with the
negative pressure valve, or if the valve opening pressure is out
of the standard range.
SLC756AA
CHECKING COOLING SYSTEM FOR LEAKSNLLC0054S04To check for leakage, apply pressure to the cooling system with a
tester.
Testing pressure:
157 kPa (1.57 bar, 1.6 kg/cm
2, 23 psi)
CAUTION:
+Higher than the specified pressure may cause radiator
damage.
+Be sure to perform the inspections after cooling down the
engine.
+Use a hose adapter between the cap tester and filler neck
to prevent the radiator filler neck from deforming.
+If any abnormalities are found, repair or replace the malfunc-
tioning parts.
Water Pump
REMOVAL AND INSTALLATIONNLLC0055CAUTION:
+When removing water pump assembly, be careful not to
get coolant on drive belt.
+Water pump cannot be disassembled and should be
replaced as a unit.
+After installing water pump, connect hose and clamp
securely, then check for leaks using radiator cap tester.
ENGINE COOLING SYSTEMYD
System Check (Cont'd)
LC-55
Page 2759 of 3051
JLC294B
REMOVALNLLC00561. Remove the undercover, splash cover (right), and accessory
belt.
2. Drain engine coolant. Refer to LC-59, ªChanging Engine Cool-
antº.
3. Support the bottom of the oil pan with a floor jack etc., and
remove the right engine mount bracket (front side of the
engine).
4. Remove the water pump pulley.
+Loosen the pulley bolts after fixing the pulley using a screw-
driver etc.
5. Remove engine mount brackets.
6. Remove the water pump.
INSPECTIONNLLC0057+Check for rust and contamination adhering to the water pump
and vane.
+Turn the pump shaft by hand, and check that the pump turns
smoothly without looseness.
INSTALLATIONNLLC0058+Install the parts in the reverse order of removal.
+Install the water pump pulley with the front mark (painted white,
used to prevent errors during assembly) facing the front of the
engine. Refer to the figure above.
ENGINE COOLING SYSTEMYD
Water Pump (Cont'd)
LC-56
Page 2765 of 3051
Overheating Cause AnalysisNLLC0070
Symptom Check items
Cooling sys-
tem parts
malfunctionPoor heat transferWater pump malfunction Worn or loose drive belt
Ð Thermostat stuck closed Ð
Damaged finsDust contamination or
paper clogging
Mechanical damage
Clogged radiator cooling
tubeExcess foreign material
(rust, dirt, sand, etc.)
Reduced air flowCooling fan does not oper-
ate
ÐÐ High resistance to fan rota-
tion
Damaged fan blades
Damaged radiator shroud Ð Ð Ð
Improper coolant mixture
ratioÐÐÐ
Poor coolant quality Ð Ð Ð
Insufficient coolantCoolant leaksCooling hoseLoose clamp
Cracked hose
Water pump Poor sealing
Radiator capLoose
Poor sealing
RadiatorO-ring for damage, dete-
rioration or improper fit-
ting
Cracked radiator tank
Cracked radiator core
Reservoir tank Cracked reservoir tank
Overflowing reservoir tankExhaust gas leaks into
cooling systemCylinder head deteriora-
tion
Cylinder head gasket
deterioration
ENGINE COOLING SYSTEMYD
Overheating Cause Analysis
LC-62