The importance of coolant
Some people believe that cooling system problems contribute from 30% to 50% of all engine failures. Coolant certainly is a vitally important component in an engine. Approximately 30% of the energy content of fuel is wasted as heat which passes through the cooling system and into the air. The coolant must transfer all that heat to the large surface area of the cooling radiator. If the heat is not removed fast enough the engine heats up abnormally, metals expand and start to make contact and failure mode begins.
Coolant performs many other functions and anti-freeze protection is a very important one. Water turns to ice around 0°C. When water turns to ice it increases in volume by around 9%. In a sealed pressure system this increase in volume means that something must move or break. Engines typically have frost plugs (aka core plugs) which are the plugs pressed into the holes where the sand was removed from the block after casting. If the coolant in the block freezes typically these plugs will be forced out which can prevent major damage to the block. However, the resulting loss of coolant can still cause catastrophic failure if the engine then overheats.
The glycol/water ratio is the most important physical property to measure and control. 100% ethylene glycol has a freezing point of around -12°C and a specific heat capacity of about half that of water. 100% ethylene glycol is not a very good coolant or antifreeze. However, a mixture of ethylene glycol and water has a much lower freezing point (around -45°C for a 60% EG mixture). Modern engine makers typically suggest a 50/50 glycol/water mixture which gives freezing protection down to around -37°C.
Glycol also assists in cooling by raising the boiling point of the coolant mix by several degrees.
Additives and inhibitors
Modern coolants contain an additive package including several inhibitors which reduce the amount of corrosion that can occur. A cooler heat exchanger has a large surface area of copper or aluminium in the cooler which runs at a high temperature. Corrosion reduces the ability of the cooler to transfer heat to the outside. A lack of inhibiter additives can cause the efficiency of the cooler to deteriorate which can allow overheating and place more stress on an engine. Terra Analytical does not have specific test methods for the huge variety of coolant inhibitors on the market. It is best to work with your coolant supplier for their advice on the specific inhibitor test method for each specific product. [For example, Terra Analytical has the appropriate coolant tests for Caterpillar coolants supplied via Terra Cat.]
Additional coolant tests included are pH and PQ (ferromagnetic particle index) and various subjective tests such as Colour, Odour, and Visible Particles.
Benefits of routine testing
Routine testing of coolants can detect serious problems that could lead to expensive engine failure if not corrected. Coolant leaks cause loss of glycol and if operators are topping up with plain water the glycol percentage can drop down to dangerous levels. In some cases, glycol can greatly exceed the recommended level which is also dangerous. Problems such as abnormal water pump wear, combustion gas leakage, or engine oil or fuel leakage can be identified before serious damage happens.