Driving a Loaded Truck in Heat and Traffic: Cooling, Coolant and Overheating Checks

It is two in the afternoon, the truck is full of furniture, the road is crawling, and the temperature needle has started to climb. Most drivers have been there once. The ones who avoid a cracked head gasket are the ones who noticed early and acted.

A loaded truck works its engine harder, and slow traffic gives the radiator less air. Both together are when overheating shows up.

Check before you load

Do this on a cold engine, in the morning, as part of your walk-round. Our morning walk-round checklist already covers tyres and lights, so add these.

1. Look at the coolant level in the reservoir. It should sit between the marks.
2. Never open a hot radiator cap. Wait until the engine is cold.
3. Check hoses for cracks, soft spots or wet patches.
4. Look under the truck for drips where you parked.
5. Check the fan belt for wear and the fan for damage.
6. Check engine oil as well. Low oil makes heat worse.

Use the coolant the manufacturer recommends. Plain water in an emergency is better than nothing, but follow the manufacturer's guidance and have a proper mix put in afterwards.

Keep the radiator breathing

A blocked radiator is a common cause. Dust, leaves and plastic bags collect on the front. Look at it and clear it gently when the engine is cold. Do not pressure-wash it hard, because the fins bend.

Do not overload the truck. Moving more than the load suits is hard on the engine and the brakes. See our piece on moving building materials without overloading the truck.

Drive for a cooler engine

• Leave a gap in slow traffic so you are not braking and accelerating all the time.
• Use a lower gear on slopes so the engine is not struggling. Our guide to driving a loaded truck down hills helps with the downhill side.
• Avoid idling for long periods in the sun with the air conditioner on full.
• If the gauge climbs, switch the air conditioner off first.

Know the warning signs

Watch for the temperature gauge rising above its normal position, steam from under the bonnet, a sweet smell, a warning light, and loss of power. Any of these means act now.

What to do if it overheats

1. Pull over in a safe place as soon as you can. Switch on hazard lights.
2. Switch off the engine, or leave it idling only if your truck's manual says so.
3. Do not open the radiator cap. It is under pressure and can burn you badly.
4. Wait until the engine has cooled, which may take half an hour or more.
5. Check the coolant level and look for leaks.
6. If you must continue, go slowly to the nearest workshop.

Tell the customer what is happening. Keep them informed, as in our guide on what to do when a truck breaks down with a customer's load.

Rest the truck on long jobs

On an intercity trip, stop at a safe place at intervals, check under the bonnet, drink some water yourself and give the engine a short break. This ties in with staying alert on a long haul.

On Sphere

When you review a job, ask about the route, distance, access and load before you accept. A long crawl in the sun with a full truck should be part of how you choose an offer or counter-offer. Sphere drivers are verified before taking jobs, and good habits like this keep your truck earning. Read drive and earn with Sphere if you want to join.