Lesson Notes By Weeks and Term v3 - Senior Secondary 2
Preventive Maintenance
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Preventive Maintenance
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Subject: Auto Mechanical Works
Class: Senior Secondary 2
Term: 1st Term
Week: 10
Theme: Safety And Maintenance
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pressure (found on a sticker inside the driver's door jamb or in the owner's manual).
Condition: Inspect for cuts, bulges, cracks, or embedded objects. Check tread depth – ensure it's not below the wear indicators.
4. Battery Check (for non-sealed batteries): Check electrolyte level in cells (top up with distilled water if low). Inspect battery terminals for corrosion (clean if necessary). Ensure connections are tight.
5. Belt Inspection: Check accessory belts (fan belt, alternator belt, power steering belt, AC belt) for cracks, fraying, or excessive looseness.
6. Lights and Horn Check: Test headlights (high/low beam), brake lights, turn signals, hazard lights, and horn for proper operation.
7. Wiper Blade Condition: Inspect wiper blades for cracks or hardening; replace if they leave streaks or chatter. at every oil change service or every 10,000 – 20,000 km.
Power Steering Fluid: Often checked at every service; changed every 80,000 – 120,000 km or 4-6 years.
D. Determining When to Top Up or Replace Oil and Water
1. Engine Oil: Purpose: Lubricates moving parts, dissipates heat, cleans engine components, provides a seal between piston rings and cylinder walls, and prevents corrosion.
How to Check:
1. Ensure the vehicle is on level ground and the engine has been off for at least 5-10 minutes (to allow oil to drain back to the sump).
2. Pull out the dipstick, wipe it clean with a rag.
3. Re-insert the dipstick fully, then pull it out again.
4. Observe the oil level between the "MIN" (or "ADD") and "MAX" (or "FULL") marks.
When to Top Up: If the oil level is below or at the "MIN" mark, add the correct type and viscosity of engine oil in small increments until it reaches the "MAX" mark. Avoid overfilling.
When to Replace: Mileage/Time Interval: Strictly adhere to manufacturer's recommendations or the general guidelines above.
Oil Appearance: If the oil appears very dark, gritty, or has a strong burnt smell, it indicates degradation and should be replaced, even if it hasn't reached the full mileage interval.
Engine Noise: Increased engine noise or tapping sounds can indicate insufficient lubrication or degraded oil.
2. Coolant (Water/Antifreeze Mix): Purpose: Dissipates heat from the engine to prevent overheating, prevents corrosion of cooling system components, and raises the boiling point while lowering the freezing point of the fluid. In Nigeria, preventing overheating and corrosion are the primary concerns.
How to Check:
1. Ensure the engine is completely cool to prevent burns from hot fluid and steam.
2. Locate the coolant reservoir (expansion tank) – it's usually a translucent plastic tank connected to the radiator.
3. Observe the fluid level against the "MIN" and "MAX" (or "COLD" and "HOT") marks on the side of the reservoir.
4. For older vehicles without a reservoir, carefully open the radiator cap when the engine is cold to check the level (ensure fluid is visible to the top).
When to Top Up: If the coolant level is below the "MIN" mark in the reservoir, top up with the correct type of coolant mixture (e.g., 50/50 distilled water and ethylene glycol-based coolant). Never use plain tap water exclusively, as it causes corrosion and scale buildup.
When to Replace: Time Interval: Typically every 2-5 years, depending on the type of coolant (green, orange, pink).
Appearance: If the coolant looks rusty, muddy, or has floating particles, it indicates contamination and degradation, requiring a flush and refill.
Overheating Issues: Persistent overheating can sometimes indicate degraded coolant not performing effectively. E. Routine Maintenance Tasks These are basic checks and tasks that can be performed regularly by a vehicle owner or operator.
1. Visual Inspection: Under the Vehicle: Look for fluid leaks (oil, coolant, brake fluid, transmission fluid).
Exterior: Check for damaged lights, mirrors, or body panels.
2. Fluid Level Checks: Engine Oil: As described above.
Coolant: As described above.
Brake Fluid: Check level in the reservoir (usually on the driver's side firewall). Ensure it is between "MIN" and "MAX". Low brake fluid could indicate worn brake pads or a leak.
Power Steering Fluid: Check level in its reservoir (usually marked "HOT" and "COLD").
Windshield Washer Fluid: Top up as needed.
3. Tyre Checks: Pressure: Check tyre pressure weekly using a gauge and inflate to the manufacturer's recommended pressure (found on a sticker inside the driver's door jamb or in the owner's manual).
Condition: Inspect for cuts, bulges, cracks, or embedded objects. Check tread depth – ensure it's not below the wear indicators.
4. Battery Check (for non-sealed batteries): Check electrolyte level in cells (top up with distilled water if low). Inspect battery terminals for corrosion (clean if necessary). Ensure connections are tight.
5. Belt Inspection: * Check accessory belts (fan belt, alternator belt, power steering belt, AC belt) for cracks, fraying, or excessive looseness. 6. *Lights A. What is Preventive Maintenance (PM)? Preventive maintenance refers to systematic inspections, detections, corrections, and prevention of incipient failures, before they develop into major defects. It involves performing routine checks, adjustments, and replacements of parts according to a schedule, rather than waiting for a component to fail. The primary goal is to minimize vehicle downtime, ensure safety, and extend the overall lifespan of the automobile. In essence, it is about being proactive rather than reactive in vehicle care.
B. Importance of Preventive Maintenance
1. Enhanced Safety: Regular checks of critical components like brakes, tyres, steering, and lights significantly reduce the risk of accidents caused by mechanical failures. This is particularly vital on Nigerian roads, where vehicle integrity directly impacts commuter safety.
2. Increased Reliability and Performance: Well-maintained vehicles are less likely to break down unexpectedly, ensuring consistent performance and reliability, which is crucial for commercial operators like "danfo" bus drivers and "okada" riders whose livelihoods depend on vehicle uptime.
3. Extended Vehicle Lifespan: By addressing wear and tear early, PM prevents minor issues from escalating into major damage, thereby prolonging the vehicle's operational life. This is economically beneficial given the cost of new vehicles in Nigeria.
4. Reduced Operating Costs: While PM has initial costs, it saves money in the long run by preventing expensive repairs from catastrophic failures, improving fuel efficiency, and reducing the need for emergency roadside assistance.
5. Improved Fuel Efficiency: Components like properly inflated tyres, clean air filters, and well-tuned engines contribute to optimal fuel consumption, saving drivers money on petrol or diesel.
6. Higher Resale Value: A vehicle with a documented history of regular maintenance is generally more attractive to buyers and commands a higher resale value.
7. Environmental Benefits: Efficiently running engines produce fewer harmful emissions, contributing to cleaner air quality. C. Lubrication Points and Intervals Lubrication is the process of applying a lubricant to moving parts to reduce friction, heat, and wear. It also helps in cooling, cleaning, sealing, and preventing corrosion.
1. Key Lubrication Points: Engine Sump (Oil Pan): Contains the engine oil, which lubricates all internal moving parts of the engine (pistons, crankshaft, camshaft, valves, bearings).
Manual/Automatic Transmission (Gearbox): Contains transmission fluid (gear oil for manual, ATF for automatic) to lubricate gears, bearings, and synchronizers.
Differential: Contains differential fluid (gear oil) to lubricate gears that allow wheels to spin at different speeds.
Power Steering System: Contains power steering fluid to lubricate components of the power assistance system.
Wheel Bearings: Packed with grease to lubricate the bearings that allow wheels to rotate freely.
Suspension Components: Ball Joints, Tie Rod Ends, Universal Joints (on some drive shafts): Often have grease nipples (zerk fittings) where grease is injected using a grease gun to lubricate articulating joints. Door Hinges, Bonnet Latch, Boot Latch, Seat Runners: Lubricated with light oil or grease to ensure smooth operation and prevent squeaks and rust.
2. Typical Lubrication Intervals (General Guidelines, always refer to manufacturer's manual): Engine Oil: Conventional Mineral Oil: Every 3,000 – 5,000 km or 3 months, whichever comes first.
Semi-Synthetic Oil: Every 5,000 – 7,000 km or 6 months.
Full Synthetic Oil: Every 7,000 – 15,000 km or 12 months (or even longer for some high-performance oils/vehicles).
Transmission Fluid (Manual Gearbox Oil): Every 40,000 – 80,000 km or 2-4 years.
Automatic Transmission Fluid (ATF): Every 60,000 – 100,000 km or 3-5 years. Some "lifetime" fluids exist, but periodic checks/changes are still advisable in harsh conditions.
Differential Fluid: Every 40,000 – 80,000 km or 2-4 years. Grease Points (e.g., Ball Joints): Typically at every oil change service or every 10,000 – 20,000 km.
Power Steering Fluid: Often checked at every service; changed every 80,000 – 120,000 km or 4-6 years.
D. Determining When to Top Up or Replace Oil and Water
1. Engine Oil: Purpose: Lubricates moving parts, dissipates heat, cleans engine components, provides a seal between piston rings and cylinder walls, and prevents corrosion. * How to Check:
1. Ensure the vehicle is on level ground and the engine has been off for at least 5-10 minutes (to allow oil to Teacher Activities: Introduction and Brainstorming (10 mins): Begin by asking students what they understand by "maintenance" and why people service their vehicles in Nigeria (e.g., "Why do commercial drivers regularly check their 'danfo' buses?"). Facilitate a brief discussion to activate prior knowledge and introduce the concept of preventive maintenance.
Lecture and Explanation (20 mins): Systematically explain the key concepts: definition of PM, its importance (using local examples like reducing vehicle downtime for commercial transporters, improving safety on busy Nigerian roads). Use diagrams or actual components (e.g., a used engine oil filter, a new one, a dipstick) to illustrate points. Visual Identification of Lubrication Points (15 mins): Use large, clear diagrams or posters of a vehicle chassis and engine bay. Point out and explain each lubrication point (engine sump, gearbox, differential, ball joints, etc.) and discuss their typical intervals. If a real vehicle or mock-up is available, visually identify these points.
Demonstration of Fluid Checks (25 mins): Engine Oil: On a cool vehicle (or using a mock-up/video), demonstrate the step-by-step process of checking engine oil level using the dipstick, explaining the "MIN" and "MAX" marks. Show examples of clean and dirty oil.
Coolant: Demonstrate checking the coolant reservoir level, emphasizing safety (cool engine). Explain the difference between topping up and replacing, and the importance of using coolant mixture over plain water.
Brake Fluid & Power Steering Fluid: Briefly point out their reservoirs and how to check levels.
Tyre Pressure: Demonstrate how to use a tyre pressure gauge and where to find the recommended pressure. Routine Maintenance Task Walkthrough (15 mins): Guide students through a checklist of routine maintenance tasks (visual inspection, lights, horn, battery terminals, belt tension). Explain what to look for in each check.
Q&A and Reinforcement (5 mins): Address student questions and reinforce key takeaways.
Student Activities: Group Discussion (10 mins): In small groups, students brainstorm and list three major problems that can arise from neglecting vehicle maintenance in Nigeria.
Diagram Labeling (15 mins): Students are provided with unlabeled diagrams of a vehicle's underside and engine bay. In groups, they identify and label at least five lubrication points and suggest appropriate lubrication intervals for each. Fluid Level Check Practice (Practical - 20 mins): Under teacher supervision and in rotating groups, students practice checking: Engine oil level using a dipstick on a provided vehicle (or a clean engine mock-up). Coolant level in the reservoir. Tyre pressure using a gauge. Safety
Note: Emphasize extreme caution when working near engines, especially regarding hot components or moving parts. Routine Maintenance Checklist Creation (10 mins): Students, in pairs, create a simple checklist for daily/weekly routine maintenance checks an "okada" rider or "keke napep" driver should perform before starting their daily operations.
Reporting and Feedback (5 mins): Selected groups present their findings, labels, and checklists, and receive feedback from the teacher and peers.
Entrepreneurship and Job Creation (Economy/Community): Understanding preventive maintenance enables students to pursue careers as skilled mechanics, diagnostic technicians, or even start their own auto repair and service centres. This directly addresses youth unemployment and supports the local economy by providing essential services for vehicle owners and commercial transport companies (e.g., fleet maintenance for ride-hailing services, "danfo" buses, or logistics companies). Road Safety and Vehicle Longevity (Community/Personal Safety): Applying PM knowledge helps to significantly reduce the incidence of mechanical failures that contribute to road accidents in Nigeria. Properly maintained vehicles are safer for drivers, passengers, and other road users. For individuals, this means safer commutes and extended vehicle life, reducing the financial burden of frequent vehicle replacement in a challenging economic environment.
Environmental Stewardship (Environment): Vehicles that undergo regular preventive maintenance (e.g., timely oil changes, air filter replacements, engine tuning) run more efficiently, consume less fuel, and produce fewer harmful exhaust emissions. This contributes to better air quality in Nigerian cities, combating pollution and its associated health impacts.