road and
Page 45
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workshop by Handyman
Benchwise: cool it (7)
NOW that I have discussed overheating and boiling, it is worth while to take a look at the opposite effect, freezing, and the engine disaster that can occur should the coolant change from liquid to solid as a result of extremely low temperature. Every schoolboy is taught that water begins to solidify at 32deg F, but not every apprentice appreciates that it can grow by approximately 9 per cent volume; this, of course, can cause havoc when it spreads through a cylinder block. When pressure builds up the only relief possible against this load will be obtained by the block fracturing and moving in sympathy with the expanding ice inside.
Anti -freeze
The water, of course, should have anti-freeze solution in if. What this does is not to raise the temperature, but to keep the coolant in liquid form and prevent the stiffening and solidifying brought on by low temperature. There are a number of brands of anti-freeze available, but all are based upon one of three main liquids, methyl alcohol, ethylene glycol or ethyl alcohol. The last two are the most commonly used, although methyl alcohol, as the strongest of the three, can give deeper frost protection, ie. protect more water per gallon.
A point to note is that the expansion rate of an anti-freeze solution is a little greater than water at the same temperature so, at 180deg F, the anti-freeze solution will have expanded by about one-third of a pint per gallon as against the quarter of a pint expansion of pure water. Thus it is important when filling up a cold system to see that adequate space is left for natural expansion; the driver who insists on topping his radiator right up each morning always finds himself several pints short next morning. Incidentally, ethylene glycol in the water raises the boiling point, whereas alcohol lowers it, thus with ethylene glycol in the system the engine can be operated at a higher temperature without boiling than either water or alcohol solutions.
Correct mix
However, it is wise to remember that ethylene glycol should always be in the water at the correct mix, as the boiling point of concentrated glycol is far above that of a safe engine temperature. With the early anti-freeze solutions there were many problems: for instance, the mixture would frequently escape from quite tight joints and hoses, it would also foam like soap, it loosens anything that would move within the block and quite often leave this debris parked in a water pump gland, and a water leak would result.
These troubles—and the worse one of wet-cylinder liner porosity--made it necessary to include an inhibitor, particularly where a steel tube radiator was involved, and these inhibiting materials were therefore organic and non-electrolytic.
In the early days there were many attempts at "home-brewing" anti-freeze solutions: salts, oils and sugar were tried out, often with disastrous results early, or some time later. In particular, salt solutions crept out and caused havoc with electrical circuits and aluminium, in addition to corrosive activity and crust formation in radiators.
Piston seizure
One plant operator used fuel oil or kerosene, and appeared to get by for quite a while, until a severe 48-hour weekend frost caught him out because, of course, water and oil do not mix but settle at different levels when cold, and the water section went solid. Anything in the form of sugar may stiffen up when cold, and fail to permit water to reach cylinder walls, resulting in piston seizure soon after starting.
Today, there are good anti-freeze solutions available which in addition to keeping the coolant in liquid form can also prevent the formation of rust, and this feature alone gives a long life of cool running and freedom from annoying scale deposits floating loose in the block. The modern water-pump gland, too, is far less liable to give trouble with anti-freeze in the system than with plain water, and stripped pumps show glands to be near perfect after many thousands of miles.