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 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:
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.
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.
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.