Autoelectrics Mobile Product Services. Shropshire UK

Engine Cooling

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Diagnosing Engine Operating Temperature Faults

An engine temperature related fault can be caused by many different electrical, mechanical or physical factors which can make diagnosis complicated.

Overheating Symptoms

Temperature guage in red,
Loss of Power,
Loss of coolant,

Problem which may occur if fault persists :

Partial or total mechanical failure due to component seizure.

Possible causes

Electric cooling fan not operating
Fault with temperature sender unit or lack of coolant.
Wiring fault between temperature sensor and controller or relay and fan.
Fault with controller or relay unit.
Fault with fan motor.
Electric cooling fan runs continuosly
Coolant temperature sensor reads hot engine may be overheating.
Faulty coolant temperature sensor.
Wiring fault.
Controller or relay fault (relay contacts stuck)
Coolant fluid level fault
Low coolant level due to lack of maintenance, overheating,
coolant loss. Pressure test cooling system and check for leaks from water pump,radiator,hoses,core plugs ,etc. Check for coolant mixed with engine oil which may indicate engine fault such as head gasket failure or cracked component. Check for coolant loss in to combustion chambers which may be indicated by a misfire.
!! Avoid opening cooling pressure cap or removing hoses with engine hot as scalding may occur !!
Coolant flow fault
Insufficient flow of coolant around system which may be caused by failed water pump operation, restriction in flow through radiator due to blockage, restriction in flow through cooling hoses caused by kinks or blockage.
Heat exchange fault
Loss of air flow through radiator due to blockage of cooling fins with dirt, restriction of air flow due to blocked air conditioning condenser.
Loss of airflow through radiator due to poor cooling fan efficiency.
Cooling system pressure fault
Engine cooling systems become pressurised during operation.
Loss of system pressure will cause coolant to boil at a lower temperature. Loss of pressure may be caused by a faulty pressure cap, or a system leak.
Excessive pressure within the cooling system may be caused by
entry of combustion gas into the cooling system due to leaks in cylinder head gasket or cylinder head cracked.
Engine operation fault
Possible fault with incorrect ignition timing.
Possible fuelling quantity fault.
Possible fuel quality fault.
Engine Lubrication Fault
Engine operating at excessive temperature due to friction caused by lack of lubricating oil. Will almost certainly lead to mechanical damage and component failure.
Braking System fault
Excessive load placed on engine causing overheating due to braking system fault ( possible brakes sticking on ).
Temperature guage fault
Temperature guage operation fault caused by faulty gauge,faulty wiring ,or faulty sender unit.

West Mercia Mechanical Services,
Shropshire
United Kingdom.
Telephone: 01743 872222
Mobile: 07703 558610

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