Preventive Maintenance, Inspection, and Repair Procedures
Chapter Introduction
This chapter covers all the competencies related to preventive maintenance (PM), systematic inspection, and repair procedures that every Heavy Duty Equipment Technician must master for the Red Seal exam. You will be evaluated on your ability to plan, execute, and document maintenance work in accordance with Canadian standards, as well as your technical judgment when faced with real-world wear conditions.
Preventive maintenance is not a simple checklist—it is a lifecycle management strategy for equipment. In Canada, operating conditions (extreme cold, abrasion, road corrosion) impose specific intervals and methods. This chapter integrates the requirements of the Canadian Electrical Code, Part I (for vehicle electrical systems), CSA B149.1 (for natural gas/propane systems), and applicable CSA standards for brakes and lifting equipment.
1. Fundamentals of Preventive Maintenance
1.1 Definition and Objectives
Preventive maintenance is a planned program of inspections, measurements, lubrication, and component replacements, performed at defined intervals (hours, kilometers, cycles) to prevent failures rather than react to them.
The three measurable objectives are:
Availability: maximize uptime.
Total cost of ownership: reduce unplanned major repairs.
Safety: eliminate risks of injury or environmental damage.
1.2 Types of Maintenance
| Type | Description | Example |
|---|
| **Preventive** | Planned, based on time or usage | Engine oil change every 500 h |
| **Predictive** | Based on measured condition | Oil analysis, thermography, vibration |
| **Corrective** | Repair after failure | Replacement of a burned-out alternator |
| **Deferred** | Detected during an inspection, scheduled for later | Minor oil leak noted, repaired at next scheduled stop |
Red Seal Golden Rule: Oil analysis is a predictive tool, not a preventive one. It can extend the oil change interval only if the program is validated by the manufacturer.
1.3 The PDCA Cycle Applied to the Shop
Plan: consult the original equipment manufacturer (OEM) manual and service histories.
Do: execute tasks in logical order (safety first).
Check: measure, compare to tolerances, document.
Act: adjust intervals if the data indicates.
2. Systematic Inspection: Methodology and Critical Points
2.1 The Three-Pass Method
For any equipment, the inspection is done in three visual and tactile stages:
25.Peripheral pass: walk around the machine, look for leaks, visible damage, tires/tracks, hoses.
26.Under-chassis pass: use a mirror and light; check pivot points, boots, mounts.
27.Engine compartment pass: fluid levels, belts, electrical connections, corrosion.
2.2 Mandatory Critical Points (by Equipment Type)
| Component | Method | Acceptance Criteria |
|---|
| **Service brakes (pneumatic)** | Measure pushrod stroke | Max 1¾ in (44 mm) for type 30; see manufacturer's chart |
| **Parking brakes** | Hold test on 20% grade | No movement after 5 min |
| **Steering** | Total steering wheel play | Max 20° for hydraulic, 10° for electric |
| **Tires** | Tread depth | Min 4/32 in (3.2 mm) for steering, 2/32 in (1.6 mm) for drive |
| **Air suspension** | Ride height, pressure | ± ¼ in of specification; max leak 4 psi in 10 min |
| **Coupling (fifth wheel)** | Jaw wear, vertical play | Max 1/8 in (3 mm) play; contact surface ≥ 75% |
| **Exhaust system** | Check for soot, noise, mounting | No leaks before the muffler; hangers intact |
2.3 Hydraulic Hose Inspection (SAE J1273 Standard, Recognized in Canada)
No hose may be twisted, pinched, or in contact with a hot surface (> 80 °C).
Bulge = internal delamination → immediate replacement.
Crack at the fitting = fatigue → replacement.
Manufacturing date: a hose stored for more than 6 years must be rejected, even if new.
Pressure calculation: A hose's burst pressure is generally 4 times the maximum working pressure. Always check the label (e.g., "SAE 100R2AT" = 2 wire braids, working pressure 3500 psi).
3. Lubrication: Principles and Calculations
3.1 Oil Classification
In Canada, use the API (American Petroleum Institute) classification and SAE viscosity:
API CK-4: modern diesel engines (post-2017), compatible with aftertreatment systems.
API FA-4: low viscosity, fuel economy, not compatible with older engines.
SAE 15W-40: standard for most Canadian climates.
SAE 5W-40: recommended for cold-weather starting (< -20 °C).
3.2 Oil Change Intervals: The 3-Factor Rule
The oil change interval (OCI) is calculated as:
OCI = Base_OCI × Usage_Factor × Environment_Factor × Quality_Factor
| Factor | Multiplier |
|---|
| Severe service (max load, short cycle) | 0.5 |
| Normal service (highway, average load) | 1.0 |
| Light service (highway, reduced load) | 1.2 |
| Dusty / extreme cold environment | 0.7 |
| High-performance synthetic oil | 1.3 |
Example: Base_OCI = 500 h; severe service (0.5) + dusty (0.7) + synthetic (1.3) → 500 × 0.5 × 0.7 × 1.3 = 227.5 h. Round to 225 h.
3.3 Greases: NLGI Consistency
| NLGI Grade | Penetration (mm/10) | Application |
|---|
| 0 | 355-385 | Low-temperature joints |
| 1 | 310-340 | Chassis, general winter use |
| 2 | 265-295 | **Standard** bearings, chassis |
| 3 | 220-250 | High-load, high-speed bearings |
Red Seal Trap: Never mix lithium and polyurea greases—they are incompatible and cause soap separation.
3.4 Correct Greasing Procedure
53.Clean the grease fitting (nipple) with a clean rag.
54.Pump until the seal or boot begins to slightly deform.
55.Do not over-grease: internal pressure can damage seals.
56.Wipe off excess grease to prevent dirt accumulation.
4. Brake Systems: Inspection and Measurements
4.1 Pneumatic Brakes — Drum Brake Adjustment
Pushrod stroke is the only reliable wear indicator. The procedure:
61.Apply the brakes (90-100 psi application).
62.Measure the stroke with a graduated ruler.
63.Compare to the manufacturer's chart (typically: type 20 = 1¾ in max; type 30 = 2 in max).
64.If the stroke exceeds the limit, adjust the slack adjuster manually or automatically.
CSA B331 Rule (Heavy Vehicle Brakes): An automatic slack adjuster (ASA) must never be manually forced unless a specific manufacturer's procedure is followed. An ASA that exceeds the maximum stroke indicates drum or shoe wear, not an adjustment fault.
4.2 Pneumatic Disc Brakes
Minimum disc thickness: stamped on the hub (typically 45 mm for a new 50 mm disc).
Runout: max 0.10 mm measured with a dial indicator.
Pads: minimum thickness 3 mm above the backing plate.
4.3 Pneumatic Circuit Leak Test
71.Charge the reservoir to full pressure (120 psi).
72.Shut off the engine.
73.Measure the pressure drop over 1 minute:
Reservoirs only: max 2 psi in 1 min.
With brakes applied: max 3 psi in 1 min.
76.Locate leaks with soapy solution (never a flame).
4.4 Hydraulic Brakes (Compact Equipment)
Check fluid level DOT 3/4/5.1 (never DOT 5 silicone in a system designed for glycol).
Boiling point: DOT 4 = 230 °C dry, 155 °C wet. Fluid contaminated with moisture must be replaced.
Bleeding: always start with the wheel furthest from the master cylinder.
5. Electrical Systems: Inspection and Measurements
5.1 Compliance with the Canadian Electrical Code, Part I
This code applies to electrical installations on vehicles and mobile equipment. Key points for the exam:
Rule 8-200: Overcurrent protection—each ungrounded conductor must be protected by a fuse or circuit breaker at the point of supply.
Rule 10-100: Grounding—the vehicle chassis may serve as the return conductor only if the connection is direct and permanent.
Rule 12-100: Conductors—wires must be supported and protected against mechanical damage; connections must be accessible.
5.2 Voltage Drop Measurements
The maximum acceptable voltage drop is 3% for lighting circuits and 10% for starting circuits.
Formula: ΔV = (2 × L × I × R) / 1000, where L = length in meters, I = current in amperes, R = resistance in Ω/km.
Example: Cable of 6 m, 15 A, resistance of 3.5 Ω/km.
ΔV = (2 × 6 × 15 × 3.5) / 1000 = 0.63 V.
On a 12 V system: 0.63 / 12 = 5.25% → too high for lighting. Use a larger cable.
5.3 Battery Testing (SAE J537 Standard)
95.Resting voltage (12 h without load): 12.6 V = 100%; 12.4 V = 75%; 12.2 V = 50%.
96.Load test (carbon pile): apply 50% of the CCA rating for 15 s; voltage must remain ≥ 9.6 V at 21 °C.
97.Conductance test: measures internal health; compare to the manufacturer's threshold (typically ≥ 70% of rated conductance).
Trap: A battery with a voltage of 12.6 V but low conductance is sulfated—it cannot deliver starting current. Replacement is justified.
5.4 Alternator and Regulator
Charging voltage at 25 °C: 13.8 to 14.4 V for a 12 V system; 27.6 to 28.8 V for 24 V.
Residual ripple: max 0.5 V peak-to-peak. Higher ripple indicates faulty diodes.
Output test: measure charging current at full load (all electrical loads on)—must be ≥ 90% of the alternator's rated output.
6. Cooling Systems
6.1 Freeze and Boil Protection
Coolant must protect down to -37 °C (50/50) or -45 °C (60/40). Use a refractometer (never a ball-type hydrometer for ethylene glycol).
| Concentration | Freeze Point | Boiling Point (15 psi cap) |
|---|
| 100% water | 0 °C | 120 °C |
| 50/50 | -37 °C | 129 °C |
| 60/40 | -45 °C | 133 °C |
| 100% glycol | -13 °C | 155 °C |
Trap: Pure glycol freezes at -13 °C—it is worse than a 50/50 mix. Never exceed 70% glycol.
6.2 System Pressure Test
110.Engine cold, system depressurized.
111.Install the pressure tester on the radiator cap.
112.Pump to the pressure indicated on the cap (typically 15 psi).
113.Hold: pressure must not drop more than 1 psi in 2 minutes.
114.Test the cap separately: it must hold pressure and release at ± 1 psi of its rated value.
6.3 Used Coolant Analysis
Rusty brown color: internal corrosion → flushing required.
Oil in coolant: defective head gasket or punctured oil cooler.
Exhaust gas in coolant: test with a gas analyzer (blue = CO₂ present) → cracked cylinder head.
pH: must be between 8.5 and 10.5. A pH < 8 indicates acidification → immediate replacement.
7. Hydraulic Systems: Inspection and Maintenance
7.1 Particulate Contamination (ISO 4406 Standard)
The ISO 4406 code uses three numbers: ≥ 4 µm, ≥ 6 µm, ≥ 14 µm.
| ISO Code | Interpretation |
|---|
| 18/16/13 | Acceptable for standard mobile systems |
| 20/18/15 | Alert limit—filter or change |
| 22/20/18 | Severe contamination—failure risk |
Counting method: laboratory or portable counter. In the shop, use the patch test for a quick assessment.
7.2 Hydraulic Oil Analysis
Viscosity: measure at 40 °C; a variation of ± 10% from the nominal value indicates degradation or contamination.
Water content: max 0.1% (1000 ppm). Water reduces lubrication and causes cavitation.
Acidity (TAN): an increase of 0.5 mg KOH/g over new oil indicates oxidation.
7.3 Filtration and Filter Replacement
Return filter: replace every 500 h or according to the clogging indicator.
Pressure filter: replace every 1000 h or if differential pressure exceeds 25 psi.
Breather filter: often forgotten—replace every 1000 h.
Clean replacement procedure:
135.Depressurize the system (engine off, accumulators discharged).
136.Clean the area around the filter housing.
137.Replace the filter and O-ring.
138.Prime the system by running the pump without load for 30 s.
139.Check for leaks and fluid level.
8. Repair Procedures: Best Practices and Safety
8.1 Disassembly/Reassembly Sequence
143.Document: photograph, label, note positions.
144.Clean surfaces before disassembly (avoid contamination).
145.Measure before disassembly (clearance, torque, position).
146.Use special tools: pullers, presses, never a hammer on bearings.
147.Reassemble in reverse order, respecting torque specifications.
8.2 Torque Principles
Dry vs. lubricated torque: a lubricated bolt requires 20-30% less torque for the same preload. Always follow the manufacturer's specification (dry or lubricated).
Torque-to-yield bolts: tighten to the initial torque, then turn by a specific angle (e.g., 90°). Never reuse these bolts.
Cross-tightening method: for cylinder heads and housings, tighten in a spiral from the center outward, in 3 passes (50%, 75%, 100%).
8.3 Welding on Heavy Equipment
Disconnect the battery and alternator before any arc welding.
Place the ground clamp as close as possible to the weld area.
Never weld on a hydraulic tank or fuel tank without complete purging and atmosphere testing.
AWS D1.1 Standard: applies to structural welds on equipment—frame repairs must follow qualified procedures.
8.4 Post-Repair Quality Control
Functional test: run the system without load, then under load.
Leak test: check all joints, fittings, connections.
Documentation: record replaced parts, measurements, torques, date, technician.
Road test (if applicable): check steering, brakes, suspension, abnormal noises.
9. Documentation and Traceability
9.1 Mandatory Maintenance Records
Each piece of equipment must have a file containing:
Service history (date, hours, mileage).
Replaced parts (part number, supplier).
Inspection and analysis results.
Certificates of compliance (brakes, lifting, pressure vessels).
9.2 Hours vs. Kilometers: Conversion
For mixed-use equipment (highway + job site), use the standard conversion rule:
1 hour = 50 km (highway use)
1 hour = 30 km (mixed use)
1 hour = 15 km (intense job site use)
Example: A truck with 4000 h and 120,000 km → total equivalent = 120,000 + (4000 × 50) = 320,000 km. Use this figure to determine the replacement interval for major components.
10. Applicable Canadian Standards
| Standard | Application | Key Points for the Exam |
|---|
| **CSA B149.1** | Natural gas and propane | Alternative fuel systems; mandatory purging before service |
| **CSA B331** | Heavy vehicle brakes | Stroke limits, performance tests |
| **CSA B620** | Fuel tanks | Inspection, pressure testing, minimum thickness |
| **Canadian Electrical Code, Part I** | Vehicle electrical systems | Conductor protection, grounding |
| **CSA Z107.1** | Audible and visual warning devices | Sound levels, light visibility |
| **CSA B354** | Elevating work platforms | Daily inspection, load test |
11. Pitfalls to Avoid
181.Confusing preventive and predictive maintenance: oil analysis is predictive, not preventive.
182.Ignoring lubricated vs. dry torque specifications: a lubricated bolt tightened to dry torque will be overloaded.
183.Reusing torque-to-yield bolts: they are single-use.
184.Measuring pushrod stroke without applying the brakes: the measurement must be taken with brakes applied at full pressure.
185.Using a ball-type hydrometer for glycol: glycol density is misleading; use a refractometer.
186.Welding without disconnecting the battery: risk of damage to electronic modules.
187.Neglecting the hydraulic breather filter: it is often the cause of contamination.
188.Confusing DOT 5 and DOT 5.1: DOT 5 is silicone, DOT 5.1 is glycol—incompatible.
189.Forgetting to depressurize the hydraulic system before disassembly: accumulators can contain residual energy.
190.Not documenting measurements: without data, preventive maintenance has no predictive value.
12. Summary
Preventive maintenance is a planned strategy targeting availability, cost, and safety.
Systematic inspection follows a three-pass method: peripheral, under-chassis, engine compartment.
Pneumatic brakes are judged by pushrod stroke, never by eye.
The Canadian Electrical Code, Part I requires conductor protection (Rule 8-200) and grounding (Rule 10-100).
Maximum voltage drops are 3% (lighting) and 10% (starting).
Coolant must be checked with a refractometer; pure glycol freezes at -13 °C.
Hydraulic contamination is measured per ISO 4406; water is limited to 0.1%.
Torque specifications must respect the condition (dry or lubricated) and the method (cross-pattern, angular).
Documentation is mandatory and must be complete, dated, and signed.
CSA standards (B149.1, B331, B620) and the Canadian Electrical Code, Part I are the legal references in Canada.
13. Final Exam Tips
Read each question twice: Red Seal examiners use negative phrasing ("except," "is not," "must not").
Use the tables: torque, pressure, and tolerance data are often provided—don't memorize everything, but know where to look.
Think in terms of safety: when a question is between two answers, choose the safest one.
Voltage drop and oil change interval calculations are frequent questions—master the formulas.
Know your standards: the exact name and rule number are required, not just the concept.
Good luck with your preparation—the same methodical rigor you apply to preventive maintenance is what will lead you to success on the Red Seal exam.
