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2nd July 1971, Page 51
2nd July 1971
Page 51
Page 51, 2nd July 1971 — road and
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Which of the following most accurately describes the problem?

workshop by Handyman

Benchwise: Cool (8)

TO A VERY GREAT EXTENT engine lubrication and cooling depend upon each other. Apart from acting as a lubricant, the oil assists in the transfer of heat, for example, from the piston to the cylinder wall, and from the oil galleries to the sump.

In order to achieve this, it is vital that the engine cooling system functions correctly. Oil and water are complementary and a failure in the water system can cause the lubrication system to overheat. Even with a full sump, any failure on the coolant side can so seriously overheat the lubricating oil that it will also begin to produce carbon-like sludge and other harmful deposits which are, in fact, chemical changes brought about in the oil by overheating.

Over-cooling

To a lesser degree, over-cooling can also interfere with the correct performance of lubrication. While I am mainly concerned here with the heavier engines, usually diesels, used in transport, it must not be forgotten that many light commercials still have petrol engines and that engine cooling is adversely affected by fuel starvation, just as over-heating can cause the petrol to vapour-lock and be generally wasteful.

Attempts at petrol economy over and above the maker's settings via smaller jets, etc, can do more than just upset the carburation. This can in fact damage valves and seats or give ring trouble, because a weak mixture raises the combustion chamber temperature. Some sporting motorists, by the way, do not realize that the exhaust system is very important in connection with correct engine temperatures, and some of this quite fancy "plumbing" can do more harm than good.

However, with all petrol engines remember the importance of the ignition side and the need for accurate timing for cool running, just as, in reverse, excessive overheating can damage spark plug insulation and electrodes. Much the same can be said for valve timing and rocker clearances, which if inaccurate can cause bad combustion, poor scavenge and excess heat. All these points have a bearing on engine cooling, and their neglect can add very considerably to the waste heat removal problem.

It should be quite apparent that just as main bearings and pistons can suffer from inadequate cooling, so can valves, guides, valve clearances, rocker shafts, etc, suffer inadequate lubrication, unequal expansion and wear when the lubrication side is subjected to excessive heat build up.

However, apart from the points needing regular service attention, the good driver also has a key part to play in the business of engine cooling. His experience will tell him when his engine is responsive and fit, and he will know equally well when he has to drop an extra gear lower than he normally does on a regular climb, and can have reason to be suspicious that his engine is going off-tune.

So much depends upon taking action when there is an early warning, and it is confirmed by changes of oil or temperature gauge readings, either singly or jointly. The driver should immediately seek advice or assistance and not attempt to nurse his vehicle home unless a cooling-down period has returned things to normal. Even then if there is undue noise or unsafe gauge readings on starting up, the engine should not be operated further. The importance of this driver/vehicle relationship cannot be overstressed, and I will devote special attention to it in a later article.

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