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