HELPING THE MECHANICS

Press, Volume LXXII, Issue 21714, 22 February 1936, Page 13

HELPING THE MECHANICS

DETECTION OP FAULTS HOW DRIVERS CAN REDUCE REPAIR BILLS If a car owner takes note of symptoms as they exhibit thfemselVeS before, after, or during the occurrence of an irregularity, he may facilitate the diagnosis and care oi the trouble by. a motor mechanic, even though he may not recognise the fault himself while noting its symptoms. The/motorißt who is unable to assist the mechanic in. diagnosing the car's trouble will probably" have a bigger, bill to pay, when the noise has been traced and cured, for the repairer, may have to drive the car 20 or even SO miles to identify and locate it. Admittedly, some irregular noises are very difficult to describe, and the circumstances in which they are prone to arise are not easy to recognise and recall. But before the car owner seeks the help of a repairer he should try to form some : ldea concerning any kind of fault, so that he can pass it on, in the hope that it will aid in diagnosis. When an, engine misfires, ior example, the driver should be careful to note the running conditions that always or usually, cause it to commence, cease, or become less or more noticeable. He should notice whether a knock'comes on when the engine is pulling or the car is over-running the engine, whether it occurs, continues, or ceases when the car is coasting with the gears in neutral, and whether it is louder or less evident as and when the engine warms up. Each of such symptoms may carry the mechanic.a little or a long way toward quick and correct diagnosis, Loose Body Bolts A bad squeak on all except very smooth roads was traced without delay on a car when the. owner was able to tell a mechanic that it always ceased for a tune after the car had been washed and soon after the car had been taken out a wet day. The body- ?„ 0 i d + mg £ 0 i te we £ e . 6 M« h tiy loose, allowing the body to "jiggle" on the chassis* but when water the cure contact surfaces it served for a while as a lubricant and stopped the squeak. + the symptoms of irregularities that should identify themsefvesto the motorist are the following cases:--When an engine misfires badly, nracticaUy ceasing to Are te soonls it at- &?"** c * rfam s Peed, Irrespective of *itJZ a ? m one •*■ f ah*y safe in dagnosing a partially-choked petrol , filter—petrol "starvation." Coll Failure If an engine has been pulling Well ana. suddenly stops -wttnout "warning, coil failure may be suspected on a car with battery ignition, particularly if the engine was running fast a moment before it ceased to fire. But if it would run at an idling speed and then stop when, an attempt was made to accelerate .it, a choked main jet would be a reasonable diagnosis. On the other hand, if pops and bangs accompanied the sudden stop, coil trouble could be ruled out at once: more likely the cause would be a floating" impediment in the passage between ihe carburetter float chamber Ignition Trouble When only one cylinder ceases to fire the cause will almost always be in the ignition—a cable adrift or a sparking plug at fault. But if all cylinders misfire regularly the contact-breaker is the first thing to inspect and test Engine knocks can- be divided into several classes—the light tapping, metallic knocking, heavy thuds and so on. Light tapping can be attributed to a loose gudgeon pin, loose pistons, or slack rings; it may also emanate from the valve gear, or the camshaft, timing gear, or- may be an ordinary carbon knock, causing pinking. Dull thudding is usually due to a slack main bearing.

Light thudding or clatter eaumafeSUa from loose big-end bearings. Tappet clearance, if excessive, produces a regular tapping, which varies* with the speed of the engine. Mfs, n -, may be traceable to wear or to fataty,;'•. adjustment. -.-:•■• *Si ii ' n " : . p n& ■ — iaiss.