MOTOR ENGINE NOISES

Wairarapa Times-Age, 23 December 1938, Page 2

MOTOR ENGINE NOISES

TRACING TROUBLES. Every motorist of any experience is familiar with the strange and unusual sounds which sometimes are developed in an engine. These may appear as squeaks, or as unnecessarily loud exhaust noises, and may lead the owner into believing that something is very radically wrong with the power unit. In most cases, however, the causes are simple, and are very easily rectified, although that, of course, does not apply to such serious thumps and knocks which very obviously are due to excessive wear in the bearings or pistons. \ The smaller noises are generallt’ caused by some slight maladjustment of the engine accessories. A most common offender is the fan belt. These days, this is usually made of reinforced rubber, and the squeaking is caused by it rubbing against the sides of the pulleys over which it runs. Frequently a cure can be effected by altering the tension of the belt. But if this is unsuccessful, the expedient of rubbing a little French chalk on the edges of the belt may be tried. This usually will stop the noise. If the owner wishes to experiment with different belt tensions, some care must be exercised. If the belt is made too tight an excessively heavy load will be placed on the bearings of the generator and water pump. A fan belt is adjusted about correctly when one side of it can be pushed in for about an inch. Sometimes a rather bad squeak is caused by the generator bearings running dry. This can very easily happen, as many motorists are apt to overlook the necessity of frequent oiling. On most generators there are two small oilers, ohe at each end, and every time the car is lubricated these should be giveh one or two drops of light machine oil. If a squeak is traced to the generator, and oiling of these bearings does not produce the desired effect, it is probable that the fault lies with commutator and the carbon brushes bearing upon it. The brushes may be worn right down so that the metal holders bear against the commutator. This is work for the sel'Vibe station, and the sooner it is carried out the better, cause running for any period in this condition is going to harm the surface of the commutator. Sometimes a squeak is due to a dry valve guide, a condition which may eventually result in a sticking valve. This rarely happens, because most engines today are provided with proper valve lubrication. It is a defiency in this direction which -causes troublh. About the most effective cure is to use some good upper cylinder lubricant in the petrol. When an engine, which hitherto has operated quietly, develops a crackling noise from the region of the bonnet, the owner may take it for granted that there is a leakage in the exhaust manifold somewhere. This hiay be cailsed by a blown gasket, there generally being one gasket for each branch of the exhaust pipe, and the cure is to replace the erring unit. But it is much more likely today, with the modern flexible engine mounts ing, that the union between the exhaust manifold and the tail pipe has loosened. •

This, it will be found generail,. is secured by two or thrbe bolts and nuts and if these are tightened the trouble ShbUld'b'e rectified. Sometimes h Copper bnd asbestos casket is Usffd at this point hfe well hs at the Uhioh of the manifold branches with thb cylinctei' blobk, ah'd in nine cases out of ten loosenihg ofthe uniofi will result in the gasket blowing otit. SO that it may be necessary to fit a new one. ’ A number bf cars us only brass or copper washers at this point, and in such a case, tightening of the nuts is all that is necessary. If one of the nuts in the union has been lost, it should never be replaced With a steel one. This will seize and rust on to the bolt under the influence of heat, and its removal will become impossible. The nut must always be of brass.