Towing when its hot; everything you need to know

As the next big hill approaches, and I see the outside temperature hovering at 42 degrees, I wonder how hot the coolant and automatic transmission oil is going to get. Towing when its hot puts a lot of extra stress on your vehicle, and you need to make sure its in tip top condition, or you’ll end up on the side of the road that’s so hot your thongs will start to melt!

Our Dmax weighs in at around 3.1 tonnes when towing our 2.2 tonne hybrid camper trailer, and they are roughly the same dimensions so air flow is pretty good.

We get hurt by the larger tyres, and the bull bar and bash plates that I’m sure hinder air flow, but it will chug along with coolant temperatures between the 90 and 105 degree mark (maximum), and around 90 – 100 degrees on the automatic transmission temperature when its seriously hot, and we’ve got it on cruise control at 100km/h.

Back it off to 90km/h and the temperatures drop back to the high 80’s and low 90’s.

Dmax and Reconn on the road
If its hot, your vehicle works much harder towing something

So, what do you need to know about towing when its hot?

If you jump in a vehicle with a big trailer on the back, and limited towing experience you can find yourself in a pickle pretty quickly. There’s a few things you should understand before you tow anything heavy when its warm; there’s enough vehicles on the side of the road on a hot day not towing, let alone loading them up with a big trailer too!

Is your vehicle actually suitable for the workload?

You’ll have to forgive me for being blunt, but there are a lot of people towing trailers in Australia with vehicles that aren’t really up to the task. The primary factor behind this is weights, with big caravans being towed by vehicles that are overweight in one way or another.

We’ve written a comprehensive towing guide that explains the 7 weights you need to comply with, and if you are overweight on any of them then you are illegal, and can have your insurance void in the event of an accident.

Beyond that, you need to think about what you are towing, and where you are going. Asking an old, underpowered 4WD with limited power to tow a 2 tonne trailer up a big hill is going to be pushing the friendship in every department, and some vehicles put simply, are not suitable for the workload.

Hybrid MDC Camper
How suitable is your tow vehicle, honestly?

What’s the winds like?

If you’ve never experienced full on head winds when towing, be very glad! We actually bumped into an older travelling couple at Cape Keraudren who told us that they won’t travel when there’s a big head wind, and it makes sense.

The head wind will make your vehicle work much harder, and you use a heap of extra fuel in doing so. I recall leaving Cape Keraudren and consuming more fuel in our Dmax than ever before, all because we were battling the wind to move forward.

Wind at Cape Keraudren
We had some shocking wind around Cape Keraudren

What condition is your viscous hub and cooling system?

Even under normal circumstances, your 4WD can work pretty hard. Beach driving is often one of the easiest ways to test how well your cooling system goes, and if its not up to scratch, you’d better be getting some work done.

Radiators have a habit of blocking, and need to be removed and thoroughly cleaned. What’s equally as important though, is your viscous hub, which drives the fan that does all of the cooling for your engine. These wear out over time, and won’t engage at the right temperature, or often slip and don’t move the amount of air that is needed to keep your engine cool. Obviously, this has some nasty effects, and is something you want to avoid.

If you want to know how to test your viscous hub, and whether it needs replacing or topping up with oil, you can read the post we wrote; viscous fan hub.

How’s your engine coolant temperature?

The easiest way to know how your vehicle is going when its hot is to monitor the coolant temperature. Most vehicles with an OBD2 port will already have this data, its just a case of getting access to it. We run an Ultragauge, which allows us to see real time what the coolant temperature is, and its quite fascinating to watch. 

Coolant temperature can take a while to rise, and then a long time to cool back down again, and if you can see what its doing, you can adjust your driving style to suit. If you are relying entirely on the factory temperature gauge, you might be in for a shock; a lot of them have a huge band of ‘acceptable’ temperature, and won’t move from their normal position until the engine is almost cooking.

We highly recommend the use of an OBD2 reader where possible, with alarms set for coolant temperature so you avoid cooking your engine. If you don’t have an OBD2 port, you can get external temperature sensors for the coolant, and a low level alarm that is also useful. 

Ultra gauge on the Dmax
We watch our temperatures on the Ultra Gauge

How’s your automatic transmission temperature?

The large majority of vehicles on the road that are towing are automatics, and it makes sense. They are a pretty incredible piece of gear, but if you don’t treat them nicely they will cause you serious issues that cost a lot of money to fix. The temperature of your automatic transmission is incredibly important when towing in hot weather, and if you don’t monitor yours, its a mistake waiting to happen.

Again, we use our Ultra Gauge to keep an eye on the temperature, and we had an automatic transmission cooler fitted externally, which has hugely reduced the temperatures.

Just towing our 1.5 tonne camper, we were seeing temperatures up to about 105 degrees, and that’s no good. The transmission cooler generally keeps it below 95 these days, which we are much happier about. We have a couple of posts that cover this in more detail: Caring for your Automatic Transmission, and should you fit an aftermarket automatic transmission cooler?

Auto cooler
Your automatic transmission gets very warm when its hot outside

Are your tyre pressures correct?

When you are working your vehicle hard (towing when its hot), everything counts, and tyre pressures are a big part of this. Getting the right tyre pressures on your 4WD is important, but also your van.

If its really warm expect these to run higher than normal, as they will absorb the ambient temperature as well. If they are too flat, you’ll work your vehicle harder than it needs to be, and if they are really flat, you can risk damaging the tyres from excess heat build up.

Tyre pressures and heat
If its hot, your tyre pressures need to be carefully monitored

Towing when its hot is entirely possible, but you need a suitable 4WD that is in good condition, and to be aware of how hard its working.

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