Protect Your Cooling System

Cooling system protection is one of the least understood aspects of vehicle maintenance. It is also one of the most critical if an engine is to provide long-term trouble-free operation.


The word "coolant" is the single most misleading word when it comes to cooling system maintenance. "Coolant" simply means a liquid that provides temperature-transferring qualities. It could be any liquid. Plain water could be described as "coolant". So beware...the word "coolant" on a product does not define its abilities accurately. Research the product carefully to ensure it provides the qualities you require. If in doubt, do not use it.

Corrosion Inhibitors

Corrosion inhibitors are chemical packages that should be added to soft or demineralised water. There are several basic formulations of corrosion inhibitors used and they have been around for many years. A good quality corrosion inhibitor will assist in the control of:

  • pH level (typically between 7.5 and 9.0)
  • corrosion of all metals
  • scale formulation
  • electrolysis
  • cavitation erosion

Note:Corrosion inhibitors have no effect on the freezing or boiling point of the cooling system.
The biggest drawback with corrosion inhibitor products is that they are not stable over extended periods and are not tolerant of hard water.

Anti-Freeze / Anti-Boil (AF/AB) Concentrate

AF / AB concentrate is usually recommended to be used between 33.3% and 50% by volume in Australia. The main advantage of AF/AB is that the glycol component increases the point at which the system will boil and decreases the point at which the system will freeze.
In general, all corrosion inhibitors work better when blended in glycol as it provides better stability for the corrosion inhibitor chemicals. In recent years the use of AF/AB has become the preference of manufacturers to combat the incidence of "hot spot boiling". This phenomenon generally occurs where the coolant comes close to the exhaust ports of the cylinder head. Steam pockets occur and, of course, heat will not transfer through steam, hence the term "hot spots". The results can be catastrophic to cylinder heads and gaskets.

Modern Vehicle Loads

Cooling systems of modern vehicles work harder than those of the past. It is of paramount importance to maintain them correctly. Remember, there is no such thing as a product that will eliminate corrosion completely. At best, it can be kept under control with care and selection of the correct protection products.

Vehicle Manufacturer Recommendations

If a manufacturer recommends AF/AB to be used in their vehicles, then there is no choice. You may say "but I'm not going to the snow". Climatic conditions are only one of the reasons for a manufacturer to specify AF/AB; refer to "hot spot boiling" in point 3 above. It can be potentially dangerous to change from AF/AB to an inhibitor if AF/AB is the recommendation of the manufacturer. On the other hand, there is no problem with changing from an inhibitor to AF/AB after flushing.

Unfortunately, too many people think a cooling system starts and finishes at the radiator. Nothing could be further from the truth as a radiator is the easiest cooling system component to repair or replace. Modern cooling systems are smaller, lighter, have to dissipate higher temperatures and are made of more complex metal alloys. Proper maintenance is essential to ensure long life of cooling system components and efficient engine operation. Bear in mind that the average cooling system circulates around 6,000 litres of coolant per hour at 60 km an hour.

Following are some helpful hints for Cooling System Maintenance

  • Change coolant products at the intervals recommended by the product supplier regardless of appearance.
  • Flush the system if the system appears contaminated or if scale build-up is suspected. It is good practice to always flush a cooling system with a quality alkaline based flushing product when replacing the coolant, and use clean, soft or demineralised water when refilling.
  • Ensure that correct mixture ratios are maintained when topping up. Failure to do so can promote corrosion due to either under or over-treatment.
  • Turn on the heater control when draining, flushing or filling a system.
  • Periodically inspect radiator hoses and radiator cap. If hoses look expanded, feel very soft, or if you can feel them crunching when squeezed, replace them.
  • Use only products that are known to meet the requirements of the manufacturer, or at least meet Australian Standard AS/NZ 2108.1.1997 Type A or Type B. If a product does not clearly state that it meets the appropriate part of this standard do not use it.
  • Periodically inspect the external fins of the radiator core. The fins and the core tubes corrode due to external contamination, leading to reduced heat transfer efficiency and possible leakage. Replace if necessary.
  • Never remove a thermostat from a cooling system to reduce the operating temperature. This practice can lead to catastrophic problems. If the engine is running hot, identify and rectify the source of the problem.
  • Do not mix inhibitor or AF/AB products. Always drain the systems and flush completely if changing to a different brand.
  • Always take particular care to ensure that all earthing points are connected, clean and making contact. This is particularly important when a vehicle is fitted with an aluminium radiator core. Failure to take this precaution can allow the coolant to become a conductor of current that will lead to destruction of the radiator core.