Show Knocks Hard to o Explain S Says ys Nash Man Diagnosing the nature and causes of at engine knocks is frequently a difficult difficult I cult matter unless the motor car can betaken bo be taken down and a a. painstaking examination examination exam exan Im ma made o of ot Its condition accordIng accordIng accord- accord Ing Ing- to C C. E. E CO Cookerly of oC tl tho t o Pacific I Nash Motor company local distributors distributors tors of ot Nash passenger cars and trucks Very Ven often oCten similar knocks occur from wholly dlf different causes explains Cookerly and for this reason listening listening listen ing ingin in during the running running- of ot the listen I en engine engine engine en- en gine often otten fails falls to reveal reveal its Its exact location However several characteristic tic knocks aid materially in hi determining irig ing the trouble The Tho spark knock Is a clear ar sharp rap elucidates Cookerly something like a a small hammer striking a steel anvil It is more moro noticeable when the engine is under heavy load Joad as when whon climbing grades pulling pulling- through heavy sand or whenever laboring in hl high h gear If It under these con conditions the J knock nock disappears when whon the tho spark is retarded it is almost certain that you have have- havea a spark knock Tho The knock due duo to excessive carbon carbonin in the engine has exactly the same sound as tho the spark knock and occurs under the thc same conditions Retarding I the tho spark does docs not however hoo eliminate the knock If It the tho engine is is' hot and continues to fire firo for a few tew seconds after atter the ignition has been beon cut out this indicates tho the pres presence ne of ot excessive excessive sive carbon deposits as particles of or carbon become incandescent and continue continue continue con con- ignition of the tho mixture ure The Tho knock caused b by a loose Joose wrist pin bearing has about the same sarno sound as sp spark and carbon knocks and willI will willbe willbo be bo more pronounced under the tho came I conditions It may a also appear If It the engine when running Idle is sud suddenly enl accelerated and then Immediately slowed downIf downIf down If It the tho knock 19 is caused by a a. to loose lower connecting rod hearing bearing the sound will be bo similar to previously mentioned e knocks but not BO so sharp and clear more clear more like a hammer strikIng striking ing on a hea heavy piece piece- of ot solid cast Iron It n. occurs under the same conditions conditions con con- as the wrist pin knock I Tho The knock from a loose piston or piston or Is called called- piston slap as it generally times but Is Ismore Ismore ismore ma may bo be noticed at all aU more pronounced when tho the engine is under load Sudden acceleration of the tho engine when running running- Idle will produce nn yn unmistakable rattle which will usually usually usually ally identify this condition Loose crankshaft main bearing bearing- knocks are arc easily distinguished from form of ot deep dull thuds becoming louder when the engino engine I la s pulling heavily hea at low speeds |