Engine Overheating

Engine Cooling

Engine Overheats

Before conducting any cooling system diagnosis, ensure that the cooling system is fully understood.

1. Is coolant level correct?

NO - Allow engine to cool, top up level to expansion tank seam.
YES - Proceed to next step.

2. Is coolant in radiator frozen?

YES - Slowly thaw and drain system.
NO - Proceed to next step.

3. Is air flow through radiator restricted or blocked?

YES - Apply air pressure from engine side of radiator to clear obstruction.
NO - Proceed to next step.

4. Are there any external leaks, from coolant pump, engine gaskets or the heater unit?

YES - Investigate and rectify.
NO - Proceed to next step.

5. Are fan blades fitted correct way round, concave side towards engine?

NO - Rectify.
YES - Proceed to next step.

6. Is viscous unit operating correctly?

NO - Replace.
YES - Carry out a pressure test on radiator cap and system. Check thermostat type, operation and correct fitting.

7. Is temperature sender and gauge giving accurate readings?

NO - Substitute parts and compare readings.
YES - Proceed to next step.

8. Carry out cylinder pressure test to determine if pressure is leaking into cooling system causing over pressurizing and loss of coolant.

NOTE:
^ 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.