Q We have had trouble with engines
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boiling up. I remember that there was an article in CM stating that the by-pass hose from the thermostat should be sealed off when the thermostat is removed from its housing. Could you explain why?
A The by-pass should be blanked off if the
thermostat valve is removed from an engine. The reason for this is that both the water passages concerned are on the returnflow side of the cooling system and if both are open at the same time, coolant will tend to circulate around the water pump impeller rather than around the entire system. This will tend to disrupt the cooling of the engine up to the point when the coolant temperature reaches boiling point. At that stage the thermo-syphon effect causes the boiling water to rush into the radiator header tank forcing the very much colder coolant into a very hot block and head. Repetition of the cycle soon results in head and or gasket trouble.
By blocking off the by-pass. the pump will be able to maintain the coolant flow in the desired direction through the block head and radiator. The fact that there will be no automatic temperature control in this condition will result in far less damage than repeated overheating.
n Is it permissible and practicable to
operate a four-axled 32-ton-gross attic on tyres which have been remoulded twice? The tyres are of the correct size and rating.
ANothing in the regulations need deter
you from using a tyre that has been remoulded twice. We can see nothing impracticable in doing so provided that the condition of the tyre with regard to tread depth casing condition and so on meets the required standards.