Engine Overheats

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 - Adjust Drive belt
YES - Continue.

3. Is Ignition Timing correct?
NO - Check Ignition Timing.
YES - Continue.

4. Is coolant in radiator frozen?
YES - Slowly thaw and drain system.
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.
NO - Continue.

7. Are fan blades fitted correctly, concave side towards engine?
NO - Rectify.
YES - Continue.

8. Is fan clutch operating correctly?
NO - Renew.
YES - Carry out a pressure test on radiator cap and system. Check thermostat type, operation and correct fitting.

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?
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 pressurizing 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 system is contaminated with coolant, suspect inlet manifold or front cover gaskets.