How to Check Your Truck’s Coolant: Essential Tips for Preventing Overheating and Costly Engine Damage

When you're managing a fleet of commercial trucks, engine health isn't just a line on a checklist — it’s what keeps your business moving. And one of the most important (yet overlooked) parts of keeping those engines healthy? Coolant.

It’s not flashy. It doesn’t get the same attention as fuel or oil. But without it, your truck’s engine could overheat, seize, and break down — sometimes for good.

At Kooner Fleet Management Solutions, we’ve helped fleets avoid thousands in damage by just keeping a closer eye on this one thing.

Why Coolant Matters More Than You Think

Coolant (also called antifreeze) isn’t just about keeping your engine from getting too hot. It regulates the engine’s temperature, prevents freezing in winter, protects against rust and corrosion, and supports overall performance.

According to the American Trucking Associations’ Technology & Maintenance Council, coolant system failures cause nearly 40% of all engine-related issues in commercial vehicles.

That’s a big number — and one that’s mostly avoidable with proper checks and routine maintenance.

What Happens If You Don’t Check Your Coolant?

The short answer: nothing good.

Here’s what can happen if your coolant runs low or becomes contaminated:

The engine starts running hotter than normal
Fuel economy drops
Internal components (like the head gasket, cylinder head, and pistons) get damaged
The engine may seize up completely, requiring a full replacement

And let’s be honest — no fleet operator wants to hear the words “engine replacement.”

One overheating incident can result in repair costs upwards of $100 to over $1,000 — not to mention the days of downtime and delayed deliveries.

How to Check Your Truck’s Coolant (Step-by-Step)

You don’t need to be a mechanic to do this right. You just need to be careful and consistent. Here's how to check the coolant the right way:

1. Wait Until the Engine Cools Down

Heads up! Wait until the engine cools down before you mess with the radiator or coolant tank cap. Hot coolant can spurt out and cause severe burns. Always check coolant levels after the engine has cooled — ideally before the day’s first drive.

2. Locate the Coolant Reservoir

In most commercial trucks, the coolant reservoir is a translucent plastic tank near the radiator or engine bay. It’s usually marked with “Min” and “Max” level lines.

3. Check the Coolant Level

Look at the fluid line through the side of the tank. If the coolant is below the minimum mark, top it off. If it's discolored (brownish, cloudy, or has particles), it's a sign the coolant needs flushing.

4. Top It Up (If Needed)

If you're adding coolant, use the correct type (your manufacturer will specify this — don't guess). Don’t mix coolants, and never use just water unless it’s an emergency.

5. Check for Leaks

If your levels keep dropping fast, something’s wrong. Inspect under the truck and around hoses or radiator parts for signs of a leak. You can also have it tested as part of your regular Fleet Maintenance and Repair Services.

Bonus Tip: Watch the Temperature Gauge

If your driver notices the engine temperature creeping up while driving, that’s a sign something’s off — especially if it happens on a flat road or in normal weather. Don’t ignore it.

At Kooner Fleet Management Solutions, our Last Mile Maintenance service teams are trained to respond fast to such warning signs and provide fixes before the engine takes a hit.

How Often Should You Check Coolant?

Every truck is different, but here’s a good general rhythm:

Coolant level: Check weekly (daily if trucks run in extreme heat or high mileage routes)
Coolant quality: Check monthly or during oil changes
Coolant flush: Every 2 years or every 80,000 to 100,000 km, depending on vehicle and coolant type

Better yet, automate it. With fleet management solutions and smart sensors, you can monitor coolant levels, temperature spikes, and service needs in real time.

What to Look for in a Coolant Maintenance Plan

When it comes to coolant, prevention is way cheaper than repair. Here’s what a good fleet management service should help with:

Scheduled coolant checks
On-site coolant top-ups
Full system flushes
Leak inspections
Alerts for abnormal temperatures
Engine diagnostics via telematics

Whether you manage 5 trucks or 50, this kind of upkeep can save you a fortune in the long run.

Final Thoughts: Don't Let Coolant Be an Afterthought

Coolant isn’t glamorous. It won’t be the star of your dashboard or maintenance checklist. But if you ignore it, the price is high — both in terms of engine wear and road downtime.

Regular checks take minutes. Replacing a damaged engine takes weeks.

Need Help Keeping Cool Under the Hood?

Kooner Fleet Management Solutions has your back. Our team can handle everything from routine coolant checks to complete truck and trailer repairs. With tools like real-time diagnostics and reliable roadside assistance service, your fleet stays cool, even when the pressure's on.

Let’s talk about a coolant service plan that fits your routes, budget, and fleet size. Click here to book a maintenance check or speak with one of our experts today.