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29th October 1971
Page 90
Page 90, 29th October 1971 — road and
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workshop by Handyman

Benchwise: cool it (25)

IT IS worth while looking a little further into the business of anti-freezing precautions because an otherwise successful winter season of fleet operating can be upset by lack of attention to detail. The fact is that in many a busy transport garage the tools used for testing various items may be used continuously with little regard to their condition. There is nothing more alarming to the engineer having his vehicle tested for anti-freeze strength, than to see that the hydrometer being used is probably unable to register correctly because it is not clean.

Dirty float

If the inside of the hydrometer's glass barrel is dirty and semi-adhesive the float will have no chance of sensing the exact value of the solution even if the float is not in such a glued-up state that it will resist movement. A syringe is constantly taking samples from the top of radiators where the liquid drawn off can be contaminated with several assorted acids or chemicals each of which can leave a coating inside the hydrometer. Therefore clean out the hydrometer and its float at regular intervals; check the accuracy of the instrument from time to time, by taking readings of prepared solutions of a known anti-freeze protection.

For information purposes. in a solution of one-third anti-freeze and two-thirds water, ethylene glycol anti-freeze gives protection to zero. ethyl-alcohol will protect to + 2deg F, and methyl alcohol gives protection to — l2deg F. In a solution of half anti-freeze and half water the protection figures would be ethylene glycol —34deg F. methyl alcohol —48cleg F. and ethyl — 23deg F.

Certain properties of anti-freeze solution differ from those of water, and these differences have a bearing on cooling system preventive maintenance. Adding anti-freeze to water lowers the freezing point of the water in proportion to the amount added. In the case of ethylene glycol anti-freeze the lowest possible frost protection of —62deg F is provided by a solution containing 60 per cent anti-freeze and 40 per cent water.

However, the main point to remember when mixing anti-freeze is that the manufacturer's directions should be followed in all details.

It should be noted that alcohol anti-freeze solutions boil at very much lower

temperature than v7t7r, whereas ethylene glycol solutions have higher boiling points than water, and of course this permits a higher engine temperature without boiling. However, ethylene glycol could not be used pure, as it has a boiling point far above safe engine working temperatures and would be unsafe as a coolant without water added.

Evaporation does not affect anti-freeze — any loss will be found to be caused by leakage. One problem noted with anti-freeze, especially when it is old and well used, is foaming; this is also brought on by impurities in the water from natural minerals. The coolant does not froth. but takes, a generally milky appearance owing to air bubbles. This air does not help cooling at all, although it does increase the coolant volume. As I explained earlier, air in the coolant is undesirable and reduces the ability of the coolant to transport heat away from the engine.

Evaporation

Although anti-freeze is a searching liquid and will find a way out past a slack hose-clip or joint, its rate of escape will bc no greater than water, although ethylene glycol mixtures always give the impression of high loss at even a small leak. The reason for this is that ethylene glycol evaporates more slowly than water and always leaves a strong trace.

On the other hand, alcohol mixtures evaporate more quickly than water and leave less trace. The one and only answer to anti-freeze leakage is proper inspection and attention to maintenance detail; and if this is done before and when the anti-freeze is installed, there is no reason for any leakage to occur during winter.

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