Cooling 5 - Coolant
|Tasks of cooling|
|Despite anti-freeze good heat transport capability|
|Gentle handling of gaskets, hoses|
|No corrosion of metal parts|
|Avoidance of the gaseous state|
First and foremost the cooling has the job of carrying excess heat from the internal combustion engine to the radiator and to the interior heating of the vehicle. In addition, possibly also the heat developing from the oil circulation, the exhaust gas recirculation and from the automatic gearbox. Also at low temperatures the cooling should be ready for operation and for protection of the system against corrosion. The condenser of the air-conditioning and of the intercooler can also often discharge their heat directly into the open air.
Coolant consists only perhaps half of water with a low lime content. Thus, one no longer speaks of water cooling, but of liquid cooling. A number of additives, e.g., against corrosion, are also used in summer. No later than at the beginning of the cold season, the density of the coolant and also the amount of anti-freeze should be checked. 40-50% is normal. As one can see from the above diagram, with an amount of more than 60% anti-frost, the security against freezing once again becomes less. Very often only a certain anti-freeze is permitted by the manufacturer. Sometimes one can even tell by the colour, that two coolants are not compatible with each other.The engine needs protection against frost, because water (apart from the metals, bismuth and gallium) has the characteristic of expanding when freezing to ice. Then, below 0°C it contracts more than comparable substances, apparently to balance itself with the other substances. This would however, be of no use to the cast iron- or also aluminium cylinder block. Just as freezing water can even split mountains, it would just as easily crack the cylinder block. Although there are some engines which have a frost plug which will yield to the pressure first, but nobody should count on it. This is why, e.g. C2H6O2 (Ethylene-glycol) is added to the coolant. Other possible additives are inhibitors and colouring.
Coolant must be disposed of as a heavy metal-containing waste. 08/11