road and
Page 35
If you've noticed an error in this article please click here to report it so we can fix it.
workshop by Handyman
Benchwise :
cool it (10) NOW that I have outlined certain reasons for driver tuition on cooling, it will be as well to indicate some of the worst things that can happen as a result of neglect, indifference to change, or just plain lack of knowledge. I have already shown how overheating can cause engine destruction. When an engine is taken way above its normal operating temperature it can begin to knock and suffer lubrication failure which will not only add to the overheating, but will hammer out bearings, cause piston ring break-up, unequal expansion of close-fitting items, and very rapid wear of all moving parts—consequently a serious loss of power must soon develop.
A worse feature, however, is that which is all too often the initial cause of the trouble when the engine has begun to heat up past its normal temperature, and when this rise has gone unnoticed or ignored by the driver until the vehicle comes to a steaming halt. Already there may be bare areas in the water jackets around head and block and some distortion occurring.
Topping-up danger
The serious danger lies in any immediate attempt to top up the radiator before the overheated areas can cool and settle down to normal, as the arrival of cold water on these parts can cause cracking and thus severe leaks, or warping of cylinder head or block faces, making it no longer possible to seal down fully on the gasket. The only thing to do in this case if you are lucky and the damage is not too serious, is to undertake a strip down for a refacing operation; the alternative' s a new block or head.
So it is most important that drivers are made fully aware of the 'risks that go hand in glove with any hurried topping up, following a boiling incident. Earlier, I wrote about the danger in operating an over-cool engine, which may not be quite so severe as in overheating, but causes damage just the same if not till a little later on.
Operating at a too low temperature and particularly in winter weather can result in excessive fuel consumption, usually from unburnt fuel and above normal throttle opening, thus the unburnt fuel will bring on engine oil dilution over a period, although the earlier effect can be piston ring wear through the washing-out effect of raw fuel passing down the bores. This again is detrimental to the engine in that the low temperature will cause condensation and water will begin to collect, thus in a short time sludge will form, adding to the lubrication problem. This sludge will collect in oil galleries, particularly in the crankshaft oilways between main and big-end journals and the result can be bearing failure of some magnitude. Just to add to the general bother building up, partly burnt fuel vapours mix with the water and form into a corrosive acid that will attack and mark engine parts, bearings, cam followers, etc. So while the risk of overcooling is somewhat less than overheating particularly in Britain where heaters are in regular demand and a cold engine will soon arouse the driver's attention, nevertheless, damage can be caused where this feature is permitted to arise. Both the driver and the service mechanic should periodically check that the engine does reach and hold its normal heat.
With this latter feature still in mind and with regard to the diesel engine in particular, additional thought is called for in cold weather as the overcooling problem can arise from a long warm-up at idling speed, owing to bad combustion.
Similarly, an engine left idling to keep hot water for the cab heater, for instance, during a long wait on some cold dockside can be running far below the heat needed for correct combustion and waste fuel can be setting up the dilution and condition I mentioned earlier. This is one of the hazards facing operations in winter, when it is quite common for drivers to leave the engine idling to keep screens clear of ice and mist, ready for a quick move when called.
There are two solutions here. One is that in order to keep engine clear of this unburnt fuel problem they should not be allowed to idle for long periods. Instead, any warming up should be done at brisk revs to guarantee clean combustion; the engine coolant will be warm in far less time and at no risk of unseen trouble. The other is that for vehicles on regular dockside duty, or those which must queue up anywhere in winter, suitable radiator blinds should be fitted by the engineers, but their use restricted to those standing times, unless the operator is willing to spend extra money on thermo-controlled blinds.