Presentation on theme: "CHAPTER 3 n LUBE AND COOLING SYSTEMS. CHAPTER OBJECTIVES n Analyze wear & damage to Lube & cooling parts. n Explain Lube & cooling system theory. n Select."— Presentation transcript:
CHAPTER OBJECTIVES n Analyze wear & damage to Lube & cooling parts. n Explain Lube & cooling system theory. n Select & perform the most appropriate repairs.
CHAPTER INTRODUCTION n Failure of the Lube system will lead to engine failure. n Failure of the Cooling system will lead to engine failure. n Periodic maintenance is vital to dependable operation.
THE LUBRICATION SYSTEM n Lube system is least understood area of engine repair. n Proper lubrication is achieved only by the distribution of clean oil under pressure. n Oil pressure is created only when there is a resistance to flow. n Excessive clearance will result in insufficient oil pressure.
OILOIL n Oil is used to reduce friction. n All moving parts are separated by a thin film of oil. n If oil is clean there is very little friction. n A few seconds without oil is equivalent to hundreds of freeway miles. n Oil cools, cleans, and prevents rust in the engine. n Oil helps seal piston rings and fills hydraulic lifters.
ADDITIVESADDITIVES n Oil additives are consumed during use. n Temp above 250 F will cause excessive oxidation & varnish buildup.
ANTIOXIDANTSANTIOXIDANTS n Work to prevent the build-up of varnish and to prevent the oil from breaking down into harmful substances that can damage bearings.
VISCOSITY INDEX n Oils ability to resist change is called its viscosity index. n Oil with a high viscosity index will thin out less when heated. n Viscosity index improvers are synthetic polymers.
POUR POINT DEPRESSANTS n Lowest temp oil will flow is its pour point. n Pour point depressants lower point oil will flow.
ANTI-WEAR ADDITIVES n Zinc dithiophosphate n Open exhaust valves against 1200 PSI
CORROSION INHIBITORS n Corrosion Inhibitors combat the acid formation. n Rust protection additives prevent rust. n They displace moisture from metal surfaces. n They neutralize any acids that accumulate in the engine.
SERVICE RATING n API service rating S for spark fired engines. n API service rating C for compression fired engines. n All ratings are backward compatible. n Current rating is SH, to be replaced with SJ in January 1998.
ENERGY-EFFICIENT OILS n ATSM certifies this rating to oils that save 1% to 4%. n The container will state “Energy Conserving II” on label.
VISCOSITYVISCOSITY n The resistance of oil to flow is viscosity. n The thickness is also called weight. n When a “W” accompanies the rating, it has been tested at 0 F. n The “W” means winter, not weight.
RECOMMENDATIONSRECOMMENDATIONS n 10w - 40 is as thin as a 10w at 0 F, & as thick as a 40w at 212 F. n All domestic manufacturers recommend 5W -30 below 90 F.
DETERIORATION OF OIL n Oil never wears out, it becomes diluted with unburned fuel, water. n Note 2 aspirin tablets of dirt can cause 75,000 miles of wear. n Check gasket between air filter and carb.
OIL CHANGES n A technician can tell if oil has been changed regularly. n Oil level may be artificially high, due to water and gas. n Nitric acid causes camshaft wear. n Nitric acid reacts with zinc dithiophosphate to reduce its protective film.
CHANGING BRANDS OF OIL n If API service rating is the same, should be compatible. n Because 25% of oil is chemical additives, may cause chemical reaction.
SYNTHETICSSYNTHETICS n Synthetic oils have no waxes. n They have outstanding low temp characteristics. n They have a better viscosity index. n Drawback PRICE.
OIL PUMPS n Oil pump is driven by a gear on the camshaft. n Tree types of pumps. n External Gear, Rotor, Internal/external or Gerotor.
PRESSURE RELIEF VALVE n Controls pressure by routing oil back to pan or inlet side of pump. n Maximum pressure is controlled by the relief valve spring tension.
OIL PRESSURE n Oil pressure is a indication of condition of engine lower end. n Low oil pressure at idle can indicate excessive bearing clearance. n Low oil pressure can indicate a worn oil pump.
PUMP SCREEN n Check to be sure screen is clean.