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road and
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workshop by Handyman
Benchwise: lathe sense (27)
A SPECIFIED DIAGNOSIS procedure must be followed in order to ensure that time is not wasted. If, for example, a. defective thermostat is the cause of overheating, the preliminary diagnosis or the road test will have indicated that overheating was not preceded by coolant shortage.
On the other hand, if the thermostat was not at fault the unnecessary work involved in its removal could be avoided by following the proper procedure. The procedures for diagnosis of overflow loss and for overheating not preceded by coolant shortage, provide quick methods for locating the cause of these conditions. The easier operations are performed first and the more common causes of overheating trouble investigated early on, so that the necessity of reinstating a part removed earlier for testing will be avoided.
Trouble located After the trouble has been judged to have been located and cured a final road test should always be made to ensure that all causes of overheating have been removed. Take the fairly simple fault caused by a broken fan belt; this may have taken place on a steep hill under full power, with the boiling stirring up the sludge and rust debris in the water jacket and leading to a clogged radiator. In this instance, replacing the broken belt will not cure the overheating problem.
In a rust-clogged system the thermostat can be defective, or the water distributor tube corroded, and in such cases the cooling system can be cleaned or even the radiator replaced without the other cause of the overheating being corrected. Damage to the thermostat by severe overheating usually leaves the valve standing permanently open, and if this fault is not rectified at the time, the main cause of overheating wi/i have been corrected, but overcooling of the engine will result. Therefore the final road test is of the utmost value.
Preventive measures Since downtime is costly, it is worthwhile hastening — and simplifying — trouble-shooting for overheating oi overcooling; and unnecessary expense, time and effort can be avoided by narrowing down the search by logical step-by-step procedures.
Our first purpose has been to diagnose trouble and then correct it — systematizing our approach can be used just as effectively l'or preventive maintenance. For instance, investigations when a driver has reported the need for regular additions to his coolant will get an operator to the cause of the :rouble before serious overheating damage xcurs. In the same way, when the :emperature gauge first begins to indicate igher or lower temperatures than usual, but without any change in the vehicle operating :conditions, possible overheating difficulties Ind later loss of vehicle use may be avoided )y a system of preventive trouble-shooting, is follows: itep No. I, engine stopped: visual nspection; No. 2, tests with engine running md catchpot in use; followed by the irocedures for (A) overflow loss; (B) akage loss; (C) no shortage; and (D) over-cooling — backed. by the final road est.
Jext week: diagnosis procedure.