Fixing 4WD Cooling System Problems

Michael Borg — 1 May 2015

When you’re in the middle of nowhere, the last thing you want is for your engine to overheat and call it quits. Things such as soft sand, heavy loads and hot climates can really get your engine working overtime, which really puts your 4WD’s cooling system to the test.

So, to help catch and fix cooling issues while you’re out on the tracks, here are some proven tips, tricks, techniques and fair-dinkum bush fixes to get you back out there exploring once again.


If you snap your water pump belt, there are a few ways to construct a makeshift belt. The material you use needs to have enough grip to rotate the pulleys, and needs to be durable enough to be tightened up without stretching and breaking.

One proven material to use is some old pantyhose – simply twist them up, wrap them around the pulleys nice and tight, and tie the ends together. Alternatively, a leather belt, dog lead, bailing twine or a nylon strap will get the job done. Remember to back the adjusters off before you start so you can adjust it tighter after your tie the knot.


There are a few different options when it comes to patching up a leaking hose, but one of the simplest methods is the old soft drink can trick. Simply cut the can into a strip, wrap it tight around the punctured area and secure it with hose clamps or even cable ties if needs be. Adding a dab of sealant on top works a treat, too! Another technique is to cut the punctured bit out and re-joint the hose via a pipe with hose clamps.


Believe it or not, some factory temperature gauges aren’t designed to give you an accurate reading. In fact, the needle on your typical 80 Series LandCrusier gauge will sit around halfway, while the actual temperature could really range anywhere from 40-100°C.

Manufacturers do this so we don’t get too concerned about normal, momentary spikes in temperature. However, it means your engine could be running hotter than usual, and you wouldn’t have a clue until it overheats. Fitting a secondary aftermarket gauge means you can monitor exactly where your engine temps are at, and catch a potential problem early.


If a stick manages to fling up and damage your radiator’s main tubes (they hold the water) you’ll end up with a leak. For smaller punctures, you might get away with smearing some sealant or epoxy putty over the hole. However, for badly damaged tubes, you’ll most likely have to remove the radiator to gain better access. The idea is to sever the damaged tubes in half, roll up the ends and reseal. Then use sealant or epoxy putty to keep it wound tight.


The purpose of a thermostat is to regulate the flow of the water in your engine’s cooling system. It does this by blocking the flow altogether when the engine is cold so the water does not circulate through the radiator and get cooled by the flow of air. As the engine heats up, the thermostat opens and allows water to circulate through the radiator for cooling. This means that both the inlet and outlet coolant hoses should be hot to touch when the engine is at operating temperature.

If one of the hoses is hot and the other is still cool, it indicates that the thermostat is stuck closed. To get you out of trouble, the easiest fix is to simply remove the thermostat altogether. In fact, in most cases, the engine will run cooler than it ever has – too cool to be a permanent modification.


A tell-tale sign that a blocked radiator is causing your overheating issues is when your temperature creeps up while you’re driving at highway speeds (80-110km/h). The airflow at these speeds should generally be enough to keep the coolant cool.

If you’ve been rolling through thick spinifex (especially up north) remember to give the front of the radiator a blast with compressed air when you get back to camp.

And, if you’ve been playing in the mud, give it a thorough clean with fresh water (using a Gurney will damage the radiator fins). Oh, and if you’re running a large set of spotlights on the bullbar, try removing them as they can block the radiators surface area and restrict more airflow than you’d think.


Now, we all know that tyre pressures are a big part of 4WDing, but did you know that tyre pressure can have an effect on how hot your engine runs? Yep, it’s true — especially when you’re tackling soft sand for a prolonged period of time. An experiment I performed proved that lowering my tyre pressures by 5psi allowed my engine to run 14°C cooler!

How does it do this? Well, lower pressures create a larger tyre footprint, so tyres float across the top of the sand instead of digging down and making your engine work harder.


Turn your heater and fan on full — it sounds crazy but hear me out. The heater basically redirects engine and engine bay heat to the outside of your vehicle. Turn your air-conditioning off, as it places more load on your engine.


If you end up facing a cooling system problem out in the scrub, you’ll need to access each situation on its own merits, as every vehicle is different, and every terrain adds a whole new challenge to overcome. Start with the basics and use a bit of common sense. Work out whether the vehicle is drivable or needs to be towed. If you’re going to risk driving it, lighten the load, throw the camper on the back of your mate’s 4WD, ensure the coolant level is topped up, remove the spot lights and bug catcher that almost always block the wind from penetrating your radiator, and wait to travel when it cools off in the arvo. With a bit of knowledge and some creativity, you could get yourself back on track and back in the game in no time at all.

Check out the full feature in issue #88 May 2015 of Camper Trailer Australia magazine. 


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