The Cooling System - Radiator Failure and Repair

The cooling system is designed to prevent overheating by transferring and dissipating the heat generated by fuel combustion in the engine.

This is achieved by creating and circulating a water jacket around cylinders and head, passing the excess heat from engine to water and finally removing it by passing a current of air over a huge surface area created by a set of thin metal fins of a radiator (Incidentally the heat is transferred mainly by convection not radiation)

Radiators are usually filled with a mixture of water and a glycol-based anti-freeze. Most cooling system failures can be attributed to poor radiator maintenance and could be prevented with regular maintenance and occasional professional inspection.

Common radiator problems

Leaking fittings or seams

Parts age, corrode and wear with the normal regular daily use of your vehicle so the polymer or rubber hoses, hose clamps, bonded seams, and secondary system fittings such as an automatic transmission oil cooler will eventually fail. Check for heavily corroded or rusted clamps, for splitting or leaking seams where the cores join the tanks, and nipped, split or brittle and cracking hoses.

Radiator Fin Corrosion Damage

The thin metal radiator fins are continuously exposed to road salt, water and dirt.
At the very least; dirt build up will dramatically reduce the cooling efficiency of your radiator by forming an insulating film on the fins reducing air flow and heat transfer.

Also, the particles of dirt and salt can form corrosion points by a process of electrolysis where a microscopic battery forms. Once initiated this type of corrosion can eat rapidly through the radiator wall and cause pin-hole leaking.

Mechanical damage caused by bending the radiator fins, stone impact etc can also initiate micro-cracks in the metal surface. Salt, water and the presence of any dis-similar metal or particle can then cause rapid corrosion and crack propagation.

Radiator Bond Failure

Radiator cores can be bonded to the primary tank using solder or epoxy and create common points of corrosion or stress failure in radiators. The radiator undergoes extremes of temperature every time the vehicle is used. This causes rapid expansion and contraction of the radiator material and will tend to fail at any weak point where the expansion-contraction forces are magnified.

Electrolysis Failure

Dirt in the radiator fluid or the use of water high in dissolved minerals - especially transition metals can eventually cause scaling and sediment build-up inside the radiator. This build up occurs by electrolysis where the radiator forms a giant wet-cell battery.

Specially designed chemical radiator cleaners can be used to remove this build-up but cannot replace the metal removed from the radiator by electrolysis.

Tank Cracking

Sometimes caused by corrosion and sometimes Stress-Fatigue cracking. Some modern radiators have removable tanks that can be replaced.

Radiator Fan damage

When there is insufficient air-flow to remove the excess heat a thermostat turns on an electric fan to increase airflow and cool the radiator. A loose or damaged fan can hit against the radiator when the car goes over a bump or changes direction.

Thermostat Failure

When the engine is idling and the vehicle is stationery or in slow moving traffic there is insufficient air flow to keep the engine cool. Thermostat Failure will prevent the cooling fan from being engaged and will lead to overheating. Thermostat or Fan Failure can be easily checked by letting the car warm up and stand for a few minutes it should be possible to hear and see the fan being engaged.

There is also a thermostat controlling the flow of cooling fluid to the engine so that the engine can reach optimal running temperature. If this thermostat fails to let coolant flow correctly it can lead to engine overheating.