Lesson Notes By Weeks and Term v3 - Senior Secondary 3
Engine Lubrication and Greasing
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Engine Lubrication and Greasing
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Subject: Auto Mechanical Works
Class: Senior Secondary 3
Term: 2nd Term
Week: 1
Theme: Engine System
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Make a line sketch of the engine lubricating system State basic lubricationdiagnosis and services to becarried out Identify and list parts thatneed to be lubricated Carry out lubricationservice.
A. Definition and Purpose of Lubrication: Lubrication is the process of applying a film of slippery substance (lubricant) between two moving surfaces to reduce friction, wear, and heat generation. In an engine, lubrication prevents metal-to-metal contact of rapidly moving components. Without adequate lubrication, an engine would seize (stop working) very quickly due to extreme friction and heat.
B. Functions of Engine Lubricants (Engine Oil): Engine oil performs several vital functions within an engine:
1. Reduces Friction: Creates a thin film between moving parts (e.g., crankshaft and bearings, piston and cylinder wall), preventing direct metal-to-metal contact.
2. Cools Engine Parts: Absorbs heat from hot engine components (pistons, bearings, etc.) and carries it away to the oil pan where it can dissipate. This supplements the engine's primary cooling system.
3. Seals Combustion Gases: Helps to form a seal between the piston rings and cylinder walls, preventing combustion gases from escaping into the crankcase and maintaining compression.
4. Cleans Engine Components: Carries away contaminants like carbon deposits, metallic particles, and sludge, keeping engine parts clean. The oil filter then removes these impurities.
5. Prevents Corrosion and Rust: Forms a protective film on metal surfaces, preventing oxidation (rust) and corrosion, especially during periods of engine inactivity.
6. Absorbs Shock: Cushions the impact between engine components, particularly in the valve train, reducing noise and wear.
C. Types of Lubricants:
1. Engine Oil: Classified by its viscosity (resistance to flow) and performance standards (e.g., API – American Petroleum Institute, ACEA – European Automobile Manufacturers' Association).
Viscosity: Indicated by numbers like SAE 10W-30 or SAE 20W-50. "W" denotes "Winter" viscosity, indicating how the oil flows at cold temperatures. The second number indicates viscosity at operating temperature. A multi-grade oil (e.g., 20W-50) behaves like a lighter oil when cold (for easier starting) and a heavier oil when hot (for better protection). In Nigeria's hot climate, multi-grade oils like 20W-50 are very common.
Oil Types: Conventional/Mineral Oil: Derived from crude petroleum, suitable for older engines or those not subjected to extreme conditions.
Synthetic Oil: Chemically engineered for superior performance, better high-temperature stability, and low-temperature flow. Often used in modern, high-performance engines.
Semi-synthetic/Synthetic Blend: A mix of conventional and synthetic oils, offering a balance of performance and cost.
Additives: Engine oils contain various additives to enhance their properties, such as detergents (for cleaning), dispersants (to keep contaminants suspended), anti-wear agents, anti-foaming agents, and viscosity index improvers.
2. Grease: A semi-solid lubricant, typically a mixture of lubricating oil, a thickener (e.g., lithium, calcium soap), and additives.
Applications: Used where oil cannot be retained (e.g., open gears, bearings, chassis points) or where components are not part of a circulating oil system. Grease provides long-lasting lubrication and helps seal out contaminants.
Types: Classified by their thickener and consistency (NLGI grade). Common types include Lithium-based grease (general purpose), Calcium-based grease (water resistant), etc.
D. Engine Lubricating System Components (Wet Sump System - most common):
1. Oil Sump/Oil Pan: A reservoir located at the bottom of the engine that stores the engine oil.
2. Oil Strainer/Pickup Tube: A mesh screen and tube located in the oil sump, which draws oil from the sump and prevents large particles from entering the oil pump.
3. Oil Pump: Mechanically driven (usually by the crankshaft or camshaft), it draws oil from the sump and pumps it under pressure through the system. Common types are gear pumps or rotor pumps.
4. Pressure Relief Valve: Located in or near the oil pump, it regulates oil pressure by opening to bypass excess oil back to the sump if pressure becomes too high. This prevents damage to the system.
5. Oil Filter: Removes impurities (dirt, carbon, metal particles) from the oil before it circulates to the engine components. It ensures clean oil reaches critical parts.
6. Oil Galleries/Passages: Drilled channels within the engine block and cylinder head that distribute pressurized oil to various moving parts.
7. Main Bearings: Support the crankshaft where it rotates within the engine block. Lubricated by oil galleries.
8. Big End Bearings (Connecting Rod Bearings): Connect the connecting rods to the crankshaft journals. Lubricated via passages in the crankshaft.
9. Camshaft Bearings: Support damage to the system.
5. Oil Filter: Removes impurities (dirt, carbon, metal particles) from the oil before it circulates to the engine components. It ensures clean oil reaches critical parts.
6. Oil Galleries/Passages: Drilled channels within the engine block and cylinder head that distribute pressurized oil to various moving parts.
7. Main Bearings: Support the crankshaft where it rotates within the engine block. Lubricated by oil galleries.
8. Big End Bearings (Connecting Rod Bearings): Connect the connecting rods to the crankshaft journals. Lubricated via passages in the crankshaft.
9. Camshaft Bearings: Support the camshafts in the engine block or cylinder head. Lubricated by oil galleries.
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0. Valve Train Components: Rocker arms, pushrods, valve stems, tappets/lifters are lubricated, often by oil splashing or by dedicated oil passages.
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1. Piston Pins/Wrist Pins: Connect pistons to connecting rods. Lubricated by splash or oil mist.
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2. Oil Pressure Switch/Sensor and Gauge/Warning Light: Monitors oil pressure. If pressure drops below a safe level, the warning light illuminates on the dashboard, or the gauge shows a low reading.
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3. Dipstick: A calibrated rod used to manually check the oil level in the sump.
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4. Oil Cooler (Optional): Found in some high-performance or heavy-duty engines, it helps to cool the oil, usually by exchanging heat with the engine coolant or ambient air.
E. Working Principle of the Lubricating System (Wet Sump): The oil pump, driven by the engine, draws oil from the oil sump through the strainer. The pump then forces the oil under pressure through the oil filter, where impurities are removed. From the filter, the clean, pressurized oil flows into the main oil gallery. Branch passages from the main gallery distribute oil to the main crankshaft bearings. Holes in the crankshaft then carry oil to the connecting rod (big end) bearings. Other passages send oil to the camshaft bearings and up to the cylinder head to lubricate the valve train components. Oil then drains back down into the oil sump by gravity, ready to be recirculated. A pressure relief valve ensures that the oil pressure remains within safe operating limits.
F. Basic Lubrication Diagnosis and Services: Diagnosis (Symptoms of poor lubrication):
1. Low Oil Pressure Warning Light/Gauge: The most direct indicator. Never ignore this light.
2. Unusual Engine Noises: Tapping (valve train), knocking (main/rod bearings), rattling, or squealing sounds often indicate lack of lubrication.
3. Engine Overheating: Insufficient lubrication increases friction, leading to excessive heat generation.
4. Excessive Oil Consumption: Can be due to leaks, worn piston rings/valve seals, or incorrect oil viscosity.
5. Blue/Grey Exhaust Smoke: Indicates oil burning in the combustion chamber.
6. Oil Leaks: Visible oil puddles under the vehicle or oil stains on engine components.
7. Dirty/Thick Oil on Dipstick: Oil that is very dark, gritty, or has a strong burnt smell indicates it's degraded and needs changing.
Services to be Carried Out:
1. Engine Oil Level Check: Regularly check using the dipstick (engine warm, turned off for 5-10 minutes, on a level surface). Add oil if below the "LOW" or "MIN" mark, ensuring not to overfill. Use the correct viscosity and specification of oil.
Example (Nigerian Context): A Danfo driver in Lagos often checks the oil level every morning before starting operations, as engine oil is lost due to wear and tear from constant stop-and-go traffic.
2. Engine Oil Change: Replace old engine oil with new, specified oil.
Frequency: Typically every 5,000 km to 10,000 km or 3-6 months, depending on manufacturer recommendations, driving conditions (e.g., heavy traffic in Abuja or Kano might require more frequent changes), and oil type. * Procedure: a. Warm up the engine slightly to allow oil to flow easily. b. Park vehicle on a level surface, engage parking brake, and raise with a jack and secure with jack stands (or use a hoist/ramp). c. Place a drain pan under the oil drain plug (usually at the lowest point of the oil sump). d. Loosen and remove the drain plug, allowing all oil to drain. Inspect the drain plug washer and replace if damaged. e. Reinstall the drain plug securely. f. Locate and remove the old oil filter (using an oil filter wrench). Be prepared for to allow oil to flow easily. b. Park vehicle on a level surface, engage parking brake, and raise with a jack and secure with jack stands (or use a hoist/ramp). c. Place a drain pan under the oil drain plug (usually at the lowest point of the oil sump). d. Loosen and remove the drain plug, allowing all oil to drain. Inspect the drain plug washer and replace if damaged. e. Reinstall the drain plug securely. f. Locate and remove the old oil filter (using an oil filter wrench). Be prepared for some oil to spill. g. Apply a thin film of new oil to the rubber gasket of the new oil filter. h. Screw on the new filter hand-tight, then tighten an additional 1/2 to 3/4 turn with the wrench (refer to manufacturer instructions). i. Lower the vehicle. j. Remove the oil filler cap (usually on the cylinder head cover). k. Pour the specified amount and type of new engine oil into the engine using a funnel. l. Replace the filler cap. m. Start the engine and run for a few minutes. Check for leaks around the drain plug and oil filter. The oil pressure warning light should turn off. n. Turn off the engine, wait 5-10 minutes, and re-check the oil level with the dipstick. Add more oil if necessary, but do not overfill.
3. Greasing Chassis Components: Frequency: As per manufacturer's maintenance schedule, typically every 10,000 km or during routine service.
Procedure: a. Identify grease fittings (nipples or zerks) on components like ball joints, tie rod ends, universal joints, propeller shaft slip yokes (on RWD/4WD vehicles). b. Clean the grease fittings to prevent dirt from being forced into the joint. c. Attach a grease gun (filled with appropriate grease) to the fitting. d. Pump grease until resistance is felt, or until a small amount of new grease oozes out from around the joint's boot. Do not over-grease as this can damage boots.
Example (Nigerian Context): Mechanics servicing Keke Napep or heavy-duty vehicles like Tipper trucks regularly grease suspension and steering components due to rough road conditions.
G. Parts that Need to be Lubricated:
1. Engine Components (Internal): Crankshaft and its main bearings Connecting rods and big end bearings Pistons, piston rings, and cylinder walls Piston pins (wrist pins) Camshaft(s) and its bearings Valve train components: tappets/lifters, pushrods, rocker arms, valve stems Timing chain/gears (if applicable) Turbocharger bearings (if applicable)
2. Chassis Components (External, requiring grease): Ball joints (upper and lower) Tie rod ends Steering linkage components Universal joints (U-joints) on propeller shafts Propeller shaft slip yoke Wheel bearings (on older systems or heavy-duty applications where they are serviceable, modern cars often have sealed, maintenance-free units). Some door hinges, hood hinges, trunk hinges.
Teacher Activities: Introduction (10 minutes): Engage students by asking questions about the importance of maintenance for vehicles common in Nigeria (e.g., Okada, Danfo, private cars). Briefly explain what lubrication is and its general importance for machine longevity. State the learning objectives for the lesson.
Conceptual Explanation (30 minutes): Explain the functions of engine oil using simple analogies (e.g., oil as "blood" for the engine, cooling like sweat, cleaning like a filter). Discuss different types of engine oil (viscosity, mineral vs. synthetic) and grease, relating them to local availability and usage patterns.
System Breakdown (40 minutes): Using a large diagram of an engine lubrication system (preferably a colored one), identify and explain each component (oil sump, pump, filter, galleries, bearings, etc.). Trace the path of oil flow through the system step-by-step. Demonstrate with an actual engine block (if available) or a dismantled oil pump/filter, pointing out features. Diagnosis and Service Procedures (40 minutes): Describe common lubrication diagnostic symptoms. Encourage students to share any experiences they or their family members have had with vehicle issues. Detail the step-by-step procedures for checking engine oil level, performing an oil and filter change, and greasing chassis points. Emphasize safety precautions (jack stands, proper disposal of used oil – connecting to environmental responsibility in Nigeria).
Parts Identification (20 minutes): List and explain the different parts within the engine and on the chassis that require lubrication. Use pictures or actual components (e.g., a ball joint, a universal joint, an engine bearing) to aid identification.
Q&A and Reinforcement (10 minutes): Address student questions. Summarize key concepts and reiterate the practical importance of the lesson.
Student Activities: Active Listening and Note-taking: Students listen attentively and take comprehensive notes during explanations.
Participation in Discussions: Students answer questions, share observations, and ask clarifying questions.
Diagram Analysis: Students study the provided diagram of the lubrication system, identifying components as the teacher explains.
Sketching: Students practice sketching the engine lubrication system in their notebooks, labeling key components.
Component Identification: If physical components are available, students handle and identify oil filters, drain plugs, dipsticks, and grease fittings.
Procedure Recitation (simulated): Students can volunteer to verbally walk through the steps of an oil change or greasing procedure, reinforcing learning.
Group Discussion: In small groups, students discuss the consequences of neglecting lubrication services, relating it to engine damage and repair costs in Nigeria.
Entrepreneurship and Local Mechanics: Students who master engine lubrication and greasing can establish or work in auto mechanic workshops (e.g., in mechanic villages common across Nigeria like Ladipo Market in Lagos or spare parts markets in Aba). They can offer oil change services, identify lubrication problems, and advise customers on proper maintenance, generating income and contributing to the local economy. This skill is directly marketable. Personal Vehicle Maintenance and Cost Savings: Knowledge of lubrication enables individuals to perform basic maintenance on their own vehicles (cars, motorcycles, Keke Napep). This reduces reliance on external mechanics, saving money on service charges, and extends the life of their vehicles, a significant advantage in Nigeria where car ownership can be a substantial investment. For example, understanding oil types helps in selecting the correct oil suitable for Nigerian driving conditions (hot weather, dusty roads).
Road Safety and Vehicle Longevity: Proper lubrication prevents engine breakdowns, which can leave motorists stranded and potentially vulnerable, especially on long inter-state journeys common in Nigeria. By ensuring engines are well-lubricated, vehicles remain reliable, contributing to safer roads and reducing the frequency of road accidents caused by mechanical failure. This also extends the lifespan of vehicles, which is crucial in a country where second-hand vehicles are very common and often need diligent maintenance.