Engine coolants

An engine coolant basically makes sure that the water in your radiator doesn’t freeze, right? Well yes it does, but it does much more than that and the other functions it performs are equally as important if not even more important than the freeze protection it offers.

The question that motorists might consider at one point is whether it is really necessary to maintain the engine coolant mixture in the engines cooling system instead of just topping up or refilling with tap water as needed. In order to answer this question it is necessary to consider what an engine coolant actually does. As already stated the engine coolant has multiple functions. This includes but is not limited to the following :
  • Protecting against corrosion – By forming a protective layer on the surfaces of the engines cooling system, thereby providing protection against aggressive elements.
  • Increasing the boiling point of the coolant mixture – This maintains the cooling systems efficiency beyond 100 degrees Celsius.
  • Preventing the coolant mixture from freezing – This ensures that the coolant mixture will maintain its working capacity even at temperatures below zero degrees Celsius and also protects the heat exchangers from mechanical damage due to the expansion of frozen coolant mixture inside the heat exchanger tubes.
  • Balancing the pH of the coolant mixture – This ensures that the pH of the coolant mixture is at the correct level and therefore prevents a corrosive condition from arising. In this regard it is necessary to note that an excessively alkaline pH is as damaging (if not more so for aluminium) as an acidic pH. Corrosion in aluminium radiators caused by an overly alkaline coolant solution i.e pH of 8.5 or higher will result in corrosion characterized by pitting while corrosion caused by an overly acidic pH will be spread over a wider surface.
  • Preventing deposits on the heat exchanger surfaces – this maintains the heat transfer capability of the vehicles radiator as well as the interior heater.
  • Preventing foaming of the coolant mixture – This is necessary because foam formation will severely inhibit heat transfer capabilities of the heat exchangers in the cooling system.
While doing all of this the coolant must remain compatible with all the different materials it will come into contact with, in the vehicles cooling system. This includes metals, plastics as well as rubber seals and hoses.

While this may sound simple enough in practice it does not work out that way. During in-house testing of a selection of engine coolants taken from the market we found coolants that turned out to be so corrosive that it was possible with the naked eye to observe pitting of the surface of a sample of aluminium submerged in the coolant within a matter of a few days.

At the same time we also found coolants that turned out to be nothing more than colored water or on the other hand contained less MEG (monoethylene glycol) than what is normal for a coolant concentrate i.e the coolant was diluted but still sold as a concentrate. This is not to be confused with a coolant sold as Premix which would not be further mixed with water when filling the coolant system. Considering this, a word of caution is necessary to any motorist or workshop undertaking to refill a vehicles cooling system. In order to be able to receive or maintain a warranty on heat exchanger parts supplied by a Silverton radiators outlet it is necessary to use only coolant approved by the vehicle manufacturers or otherwise coolant supplied by a Silverton radiators outlet via Behr Hella Service – this will be branded with the Silverton radiators branding. If it is not branded with our branding then it is not approved by us.

Another important aspect of an engine coolant mixture is the water with which the coolant is mixed. Firstly the coolant must be mixed in the correct proportions. The correct proportions can be found in the vehicle owners handbook but will generally range from 30% to 50% coolant mixed with clean water. Below 30% coolant in water there will not be adequate freeze protection so this is the absolute minimum concentration required during winter. While an increased coolant concentration provides an increase in freeze protection this is only true up to a certain limit (max 60%) after which the freeze protection will actually be compromised. At the same time excessive coolant concentration will also reduce the coolant mixtures ability to transfer heat. The bottom line here is that the coolant concentration should never exceed 60% coolant in water. The quality of the water is also an important aspect – it must be clean i.e no abrasive or abnormal corrosive impurities may be present. Remember also that in certain areas town water may be heavily loaded with chlorine which is highly aggressive towards aluminium so in this case it is recommended to use demineralised water. When a radiator or heater is being replaced it is required that the entire system will be flushed so as to remove any impurities which might presently be existing in the system. Only in this way will the engine coolant mixture be able to properly function. Lastly it must be mentioned that an engine coolant has an effective lifespan that would be affected by the quality of water with which it is mixed, the prior condition of the cooling system into which it is filled as well as the coolant concentration. In a properly maintained system the coolant additives (except when using long life coolants) will generally become depleted within about three years and it is therefore recommended that the engine coolant be replaced every three years.

To answer the question as to whether it is really necessary to maintain a vehicles coolant mixture the answer is a very definite ‘Yes’. You might be able to save some money in the short run by using plain water or by using a cheap no name brand coolant but you will eventually end up having to replace much more expensive components in the vehicles cooling system if you do so. In the end the choice is yours, but don’t say you have not been warned.