• Carburetor mixture is too lean
• Ignition timing is retarded or too advance
• Radiator tubes blocked
• Restricted air flow through radiator
• Missing or damaged radiator shroud
• Water jackets in engine block clogged with rust
• Head gasket leaking exhaust into cooling system
• Burnt valves
• Valves need adjusting
• Cracks in cylinder head
• Radiator fins not attached to tube
• Coolant leaks from hoses, gaskets or water pump
• Incorrect radiator cap fitted
• Defective radiator cap – will not hold pressure
• Thermostat stuck
• Water pump impeller slipping
• Water pump impeller worn or broken
• Excessive antifreeze in coolant mixture
• Fan belt loose or slipping
• Low coolant level
• Incorrect thermostat fitted