Eliot Silverman

Eliot Silverman

Thursday, April 12, 2012

Anti Freeze, More Complex than you might think

Your Anti Freeze (also called ‘coolant’)
It has four jobs:
1.        It keeps the engine at a constant temperature
2.       It lubricates the water pump
3.       Cool the automatic transmission oil
4.       It provides heat for the heating vents.

For coolant (water) to work, it must be able to flow from the engine to the radiator and back.  Outside air passing through the radiator cools the ‘coolant’ inside the radiator. 

An anti freeze agent (ethyl glycol) was added to the coolant(water) to keep it from freezing.  Ethel glycol lowers the freezing point of water, which is important in the winter.  Additionally, it raises the boiling point of water, which is important in the summer.  Your water pump cannot pump steam so it is very important that the coolant doesn’t ‘boil.’

Your engine gets extremely hot from burning gasoline.  To maximize gas mileage, and reduce pollution, anti freeze needs to keep your engine at a predetermined temperature, normally 275 degrees Fahrenheit.   If the temperature of the anti freezes gets too hot, the air/fuel mixture will combust too soon, and if the temperature of the anti freeze is too low, the gas does not completely burn.

The temperature of the anti freeze is controlled with a thermostat.  Your car’s thermostat is NOT an on or off type of switch.  It can open up a little, or open up a lot depending upon how much cooling is needed.  Highway driving creates more heat than stop and go driving.

One of the reasons a car overheats is the thermostat does not open up or does not open up enough.  Either way, not enough coolant is allowed to pass through it to the radiator, so the coolant overheats.

If the thermostat stays open, the anti-freeze continuously circulates through the radiator, which means it takes a long time for the engine to heat up to its normal operating temperature.  This causes excess pollution, poor gas mileage, and increases the amount of time it takes for you to get heat out of the vents.

Some of the additives in your anti freeze lubricate the water pump and others prevent impurities from accumulating inside the radiator.  Many cars have engines made of cast iron and aluminum.  With two different types of metal in water (anti freeze), ions from one metal want to go to the other metal.  This causes pitting, and if the pitting gets very bad, the anti freeze escapes the engine through gaps created by this pitting.  Manufactures add a “Dielectric Inhibitor” to their anti freeze to prevent pitting.

A few years ago GM and others introduced a “Long Lasting” anti freeze.  The old standard anti freeze (green) is replaced every two years or every 24,000 miles which ever comes first.  GM’s long lasting anti freeze is colored ‘hot pink’ and Fords long lasting anti freeze is colored ‘yellow.’  Color is added to the anti freeze so we don’t confuse one with the other.  Long lasting anti freeze, we were initially told, is replaced every 5 years or 150,000 miles which ever comes first.  When long lasting anti freeze was introduced it was considerably more expensive then ‘regular’ anti freeze.  Now they cost me about the same.

Sounds good but…..  Under normal condition a small amount of water boils out of anti freeze.  It shouldn’t happen, but it does.  This will not create a problem with the old style green anti freeze.  However, if too much water boils out of long lasting anti freeze, the long lasting anti freeze solidifies inside the engine and radiator.  This prevents the flow of coolant through the engine and radiator causing the engine to overheat.  

The solid mass can be removed, but it is an expensive repair.  Years ago I met with a GM engineer and asked him about this problem. He said GM was aware of the problem, and to prevent this from happening, he said long lasting anti freeze should be changed every two years or every 24,000 miles which ever comes first. 


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