Land Rover Repair: Overheat, coolant level, engine gaskets

Question
1991 Discovery Diesel.
hi,

Temperature gauge, occasionally climbs up to top,
and red light begins to flash,
although when dipping finger in top of expansion tank, the water is cold.

The car hasen't done anything but go to my work and back (2 miles max)

Answer
Hi Richard,

here's a checklist that will help you out:

ENGINE OVERHEATING
Before conducting any cooling system diagnosis:

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, Compressor Drive Belt
YES - Continue.

3. Is coolant in radiator frozen?
YES - Slowly thaw and drain system. See Adjustment, Coolant
NO - Continue.

4. Is air flow through radiator restricted or blocked?
YES - Apply air pressure from engine side of radiator to clear obstruction.
NO - Continue.

5. Are there any external leaks, from water pump, engine gaskets, fast idle thermostat or the heater unit?
YES - Investigate and rectify. See Adjustment, Coolant
NO - Continue.

6. Are fan blades fitted correct way round, concave side towards engine?
NO - Rectify.
YES - Continue

7. 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 10, otherwise: Continue.

8. Are the air conditioning fans operating correctly?
See Electrical Trouble Shooting Manual.
NO - Rectify.
YES - Continue.

9. Is temperature sender and gauge giving accurate readings?
NO - Sustitute parts and compare readings.
YES - Continue.

10. 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 only the coolant system is contaminated suspect a cylinder head gasket.

If both systems are contaminated, suspect the radiator.

If only the lubrication system is contaminated with coolant, suspect leakage past cylinder liner seals or cylinder head gasket.

END.

Write back if you need more help.

Best of luck,

JohnMc