Diesel Truck Maintenance

Canadian seasons are tough — and your diesel truck knows it. Whether you’re battling minus 40°C winters in Alberta or long-haul heat in Southern Ontario, your engine, fluids, and systems need year-round attention.

Seasonal maintenance isn’t just about staying on the road. It’s about keeping your diesel engine healthy, avoiding costly breakdowns, and extending the life of your truck — whether it’s brand new or a high-mileage workhorse.

This guide walks through the top 10 maintenance checks every diesel truck owner should perform by season — so you can plan ahead, stay compliant, and reduce unexpected repairs.

Are you looking for a truck? Look at our used inventory.

Why Seasonal Diesel Maintenance Is Essential

Diesel engines are built for strength — but Canadian weather extremes push them to their limits.

• Cold starts can damage injectors and batteries
• High heat strains cooling and oil systems
• Salt and moisture corrode undercarriages and sensors
• Improper fuel storage in off-season leads to contamination

By anticipating seasonal stress, you can reduce wear and tear, pass CVOR inspections, and avoid mid-season downtime.

Top 10 Diesel Maintenance Checks by Season

Here’s how to prepare your truck before each seasonal shift, with a special focus on systems most vulnerable to weather, altitude, and heavy-duty operation.

1. Engine Coolant Check (Spring & Fall)

Coolant isn’t just for hot weather — it prevents freezing in winter and overheating in summer.

Checklist:

• Check coolant levels and concentration (50/50 mix)
• Test for acidity with a coolant test strip
• Flush and refill annually or per OEM schedule
• Inspect hoses and radiator for leaks or soft spots

Pro tip: Add winter-rated antifreeze before the first deep freeze.

2. Battery Load Test (Fall & Winter)

Cold kills batteries fast — especially older ones or those near end-of-life.

• Check voltage under load
• Inspect terminals for corrosion
• Clean connections and apply anti-corrosion spray
• Replace any battery older than 3 years or below 12.4V resting

Dead batteries are the #1 winter roadside issue for diesel trucks in Canada.

3. Fuel Filter and Water Separator (All Seasons)

Diesel is hygroscopic — it absorbs moisture. That makes the fuel system especially sensitive in Canadian humidity and temperature swings.

Tasks:

• Replace fuel filter every 25,000–40,000 km
• Drain water separator regularly
• Add diesel conditioner during winter and wet spring months
• Watch for power loss or hard starts — signs of fuel restriction

4. Block Heater & Glow Plug Inspection (Fall)

Winter starting relies on strong glow plugs and a functioning block heater.

• Test glow plug resistance individually
• Check block heater plug and wiring
• Confirm it's heating by touch after 20 minutes plugged in
• Consider installing a timer to pre-warm engine

For more, see our winter prep guide for used trucks.

5. Air Conditioning System (Spring & Summer)

Don’t wait until a heat wave to find out your A/C is weak.

• Test blower speed, refrigerant pressure, and air temp
• Clean cabin filter
• Inspect compressor clutch
• Top off refrigerant as needed

An A/C failure on the road can lead to fatigue and visibility issues from fogged windows.

6. Diesel Exhaust Fluid (DEF) System Checks (All Seasons)

DEF freezes at –11°C and can degrade in summer heat.

Tips:

• Use fresh DEF only — never expired or contaminated
• Keep tanks full in winter to avoid freeze/thaw cycles
• Inspect lines for cracking or leaks
• Monitor DPF regen cycles and scan for codes

Avoiding DEF system failures can save thousands in downtime and fines.

7. Tire Pressure and Tread (Monthly / Seasonally)

Temperature impacts PSI — a 10°C drop equals ~1 PSI lost.

• Check tire pressure weekly when weather fluctuates
• Rotate tires every 40,000 km
• Inspect for cupping, cracking, or uneven wear
• Use winter-rated tires or chains where legally required

Proper tire care improves safety, fuel economy, and longevity.

8. Suspension and Steering Systems (Spring & Fall)

Canadian roads can be brutal after freeze-thaw cycles.

• Check leaf springs and bushings for damage
• Grease all fittings, ball joints, and U-joints
• Inspect tie rods, kingpins, and shock mounts
• Align wheels after every season change or long trip

This helps reduce driver fatigue, tire wear, and costly alignments.

<span style="font-weight:bold;">9. Cabin Heating & Defrost System (Fall

Visibility = safety. Always check defrosters and heaters before winter hits.

• Test fan speeds and vent direction
• Replace cabin filter
• Inspect heater core and blend door actuator
• Clean windshield vents of dust or debris

<span style="font-weight:bold;">10. Rustproofing & Undercarriage Wash (Late Fall & Early Spring)**

Salt, grime, and calcium chloride can destroy your truck’s value and safety.

• Power wash the undercarriage monthly in winter
• Apply rustproofing before snow or after spring thaw
• Check frame rails, brake lines, and fuel tanks
• Inspect for paint bubbling or flaking near wheel wells

Year-Round Maintenance Table

Here’s a quick glance at what you should check before every season in Canada:

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