Cooling Systems - Engine Cooling

Cooling System Servicing

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The combustion of petrol, diesel, lpg or other alternative fuels in your engine will generate heat. The cooling system prevents overheating by transferring and dissipating the heat using a water based cooling system.

When the engine cooling system fails to dissipate this heat efficiently, aluminum cylinder heads may warp; cylinder head gaskets can blow and the engine can seize.

Cars sitting in stationary traffic do not have enough air flow to dissipate heat effectively. If the radiator fan fails then the engine can overheat. Insufficient coolant due to leaks or evaporation losses will also reduce cooling efficiency.

The Cooling System

A circulating water-based cooling system forms a jacket around the cylinders and cylinder head absorbing the excess heat from engine and dissipating it by pumping the water through a radiator that passes a current of air over a huge heat-exchanging surface area constructed from a set of thin metal fins.

A radiator mainly dissipates heat by convection rather than radiation

Water Pump

The water pump is driven by a belt connected to the engine crankshaft. This way, the water pump can circulate coolant fluid as soon as the engine starts running.

The water pump uses spinning vanes with the fluid drawn into the centre of the pump. Coolant fluid is forced outwards by centripetal force as the vanes spin and pumped to the engine.

The fluid goes to the engine block and cylinder head first before entering the radiator to dissipate the collected heat and returning back to the pump.

Radiator Coolants

The coolant is usually a mixture of water and a glycol that prevents the water from freezing in winter. It also contains a mixture of anti-oxidants or corrosion inhibitors that not only cool but protect the engine block and circulation system components.

The corrosion inhibitors are consumed or break down over a period of time making it vital to replace the engine coolant regularly and maintain protection.

Common radiator problems

Leaking fittings or seams caused by pinhole corrosion. Bonded seams or welds where dissimilar metal contaminants may be present in the welding alloy.
General age degradation causing polymer components to become brittle leading to failure of pipes, hoses.
Wear and tear of moving parts with the normal regular daily use of your vehicle.

Corrosion causing Radiator Fin Damage

Thin metal fins making the high surface area of the radiator become contaminated with road salt and dirt. Dirt build-up insulates the fins and cooling efficiency is lost.

A mixture of localised dirt and salt can also lead to micro electrolytic cells being formed that can rapidly corrode certain metals forming pin-hole corrosion.

Impact Damage

Larger particles impacting the radiator grill at speeds up to 70mph can bend fins, initiate stress cracks that corrode causing radiator failure

Radiator Failure - Bond Failure

Modern Radiator construction may have the primary cooling tank soldered or epoxied.
Differences in thermal expansion can lead to points of stress with large changes in temperature. Rapid expansion followed by contraction over a number of heating a cooling cycles will lead to failur where the expansion-contraction forces are magnified at a weak bond area.

Electrolysis - Internal Corrosion Failure

Just as salt and dirt can corrode elements of the cooling system from the outside in; so dirt contamination or use of water with an agressive mineral content or high trnsition metal content such as copper can trigger scaling up and sedimentation to build-up inside the radiator.
The metal elements of the cooling system can form a giant wet-cell battery and corrosion failure occurs from the inside, going unseen until it's too late.

Chemical radiator cleaners can remove this build-up but don't replace any metal removed by corrosion.

Coolant Tank Cracking

Corrosion or Stress-Fatigue cracking can lead to failure. Some systems are intrinsic to the engine block while some have replaceable tanks.

Radiator Fan Failure

Insufficient air-flow causes heat to build and a thermostat switch turns on an electric fan to artificially increase airflow and help with radiator cooling.
Mechanical damage to the fan blades, fan bearing or an electrical fault can result in failure and overheating

Cooling System Thermostat Failure

A secondary thermostat monitors engine temperature so that the engine can reach optimal running temperature before pumping coolant. Thermostat failure may impair coolant flow and allow the engine to overheat.