300Tdi Discovery
V8i
1
FAULT DIAGNOSIS
ENGINE OVERHEATING
Before conducting any cooling system diagnosis:
See
Description and operation, Engine Cooling
1. Is coolant level correct?
NO -
Allow engine to cool, top up level to
expansion tank seam.
YES - Continue.
2. Is drive belt tension correct?
NO -
See ENGINE, Repair, Drive Belt -
Check Tension
YES - Continue.
3. Is ignition timing correct?
NO -
See ELECTRICAL, Adjustment,
Ignition Timing
YES - Continue.
4. Is coolant in radiator frozen?
YES - Slowly thaw and drain system.
See
Adjustment, Coolant Requirements
NO -
Continue.
5. Is air flow through radiator restricted or blocked?
YES - Apply air pressure from engine side of
radiator to clear obstruction.
NO -
Continue.
6. Are there any external leaks, from water pump,
engine gaskets or the heater unit?
YES - Investigate and rectify.
See Adjustment,
Coolant Requirements
NO -
Continue.
7. Are fan blades fitted correct way round, concave
side towards engine?
NO -
Rectify.
YES - Continue.
8. Is viscous unit operating correctly?
See
Description and operation, Viscous Fan
NO -
Renew.
See Repair, Viscous
Coupling, Fan Blades, Pulley and Fan
Cowl
YES - Carry out a pressure test on radiator cap
and system. Check thermostat type,
operation and correct fitting
See Repair,
Thermostat
If pressure test leads you to suspect coolant
leakage across gaskets, go to check 11,
otherwise: Continue.
9. Are the air conditioning fans operating correctly?
See Electrical Trouble Shooting Manual.K5
NO -
Rectify.
YES - Continue.
10. Is temperature sender and gauge giving
accurate readings?
NO -
Substitute parts and compare readings.
YES - Continue.
11. Carry out cylinder pressure test to determine if
pressure is leaking into cooling system causing
over pressurising and loss of coolant.
If problem is not diagnosed, check the coolant system
for engine oil contamination and engine lubrication
system for coolant contamination.
If the coolant only, or both systems are contaminated,
suspect cylinder head gaskets or radiator.
If only the lubrication stystem is contaminated with
coolant, suspect inlet manifold or front cover gaskets.
