Pre-Summer Cooling System Check List

Your mates mightn’t think you’re cool, but your 4X4 sure will after following these five simple cooling system tips…

Much like David Bowie and Freddie Mercury were way back in 1981, your cooling system is under pressure. And much like living the lifestyle of two high-flying celebrity musicians, things can (and will) go wrong without a little bit of maintenance from time to time. While the cooling system fitted to your four-wheel drive has an incredibly complex task to handle, the reality is there aren’t too many components involved. With the warmer months fast approaching, here are five areas of your cooling system you should investigate before hitting the tracks. After all, replacing parts in a nice clean workshop is about 16,003 times easier than on the side of the track in 40-degree heat… and I don’t know about you, but I kind of like reaching my destination at the end of the day. I know, crazy right?


Radiator coolant plays a very important part in a cooling system, yet it certainly doesn’t last forever. A good quality coolant will consist of a balance of ethylene or propylene glycol, anti-foaming agents, alkaline balance as well as rust and corrosion inhibitors. Not only does coolant need to have excellent heat transfer properties, it also needs to avoid freezing in colder climates while preventing the build-up of rust and corrosion. Never run tap water in your cooling system (unless it is an emergency); only use distilled water or even rain (tank) water. Your manufacturer will specify when to change the radiator coolant, and it is critical to meet these expectations for engine longevity. So, when was the last time you changed your coolant?


One often-overlooked cooling system component is the clutch fan assembly. Another is the actual fan itself. Fans can crack over time, and I don’t need to tell you that a sharp plastic object spinning at 3,000rpm will do damage if it decides to break. Fan clutch assemblies lose tightness – meaning when the engine needs cooling the most, there isn’t enough drive to cool the motor effectively. Some clutch fan assemblies can be rebuilt by adding small bottles viscous fluid to firm up the operation. If you are unable to rebuild the clutch unit, it’s time to dust off the credit card and pick up a new one. My GQ Patrol would always warm up climbing mountains; after replacing the fan and clutch with a new unit, the factory temp gauge now never moves. Basically, if you can spin the fan easily once the engine is warm (and switched off, naturally), it is time to investigate the topic further.


This might seem a tad simple, but checking the condition of your belts and hoses regularly could save you thousands in engine repairs. A tiny leak in the cooling hoses can drain enough coolant from the system to overheat an engine before the factory temperature gauge even has time to register. Rubber hoses will harden as they age, so if yours feel brittle it is time to replace them ASAP. It is always a good idea to keep your old ones as spares too. Belts tend to hide abuse better than hoses… the trick here is to bend the belt back on itself and look for any cracking, which is a sure sign it needs to be replaced sooner rather than later. Again, keep these old belts as spares as they could save your bacon.


A cooling system thermostat is an incredibly ingenious and rather reliable mechanical component. Please, for the love of all things sacred, don’t remove the thermostat fitted to your cooling system (as some keyboard warriors on Internet forums will recommend). The thinking from a few decades ago was that if the coolant is flowing faster, it will remain cooler. Rubbish! By running the correctly rated thermostat, coolant will remain in the radiator longer – meaning it will actually have a fighting chance of staying within operating temperatures. The thermostat assists the engine in reaching its critical operating temperature sooner, too. Without one, your engine will run rich (and not in a good way). As a side note: Before fitting your new thermostat in its housing, place it into a pot of boiling water to ensure the new component is in fact operating.


My take on radiators, is always buy the best quality and biggest radiator you can fit (and afford). A radiator is composed of a series of cooling tubes that run through the unit, which can block with debris over time. If your radiator is partially blocked, a process known as ‘rodding’ can solve this. Basically, the radiator end tanks are removed and a long sword-like device is pushed through all the tubes to clear them out. If your radiator is looking older than the Queen, it could be more cost-effective to replace it. Now, I’m a fan of brass/copper radiators as they are far simpler to repair in the bush. If you must be lured into a blinged-up alloy radiator… if it sounds too cheap then it is too cheap.


Source: Unsealed4X4

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Comments 3

  1. You didn’t mention checking the condition of the water pump, however this involves fairly major disassembly of the engine in some engines. I replaced the factory pump in a 1HD-FTE engine at 300,000 km during a cooling system overhaul, which had plastic fins, and I stress “had” as they were nearly completely worn away. The replacement come with metal fins.

    In my opinion the factory radiator is the best for the job, which does have plastic tanks, however shrouds etc fit correctly, and these shrouds aid in the cooling capability of the system. With some after market radiators the alloys used in making them can cause electrolysis (corrosion) due to dissimilar metals in the system, to occur within the engine and radiator.

    I also fitted an “Engine Watchdog” (Google It) during the above service, and I got the one with 2 readouts, where I fitted 1 transmitter to the hottest part of the engine where the coolant leaves the block at the top of the engine and the other on the thermostat housing where the coolant enters your engine from the bottom hose of the radiator. These are invaluable as they give you an audible warning at whatever temp you set and most importantly they measure block temp NOT coolant temp which varies considerably throughout its path through the engine. Further to this most factory coolant temp gauges are electronically “restricted” around the normal temp indication…. In other words large temp changes in the normal range will NOT allow the needle to move very much. By the time you notice your factory gauge going full scale high it may be too late (depending on conditions) It’s worth “googling” this to find further information. A watchdog will scream at at you at whatever temp you set each indicator.

    The temp drop of the coolant through the radiator varies between about 12 and 22 degrees depending on the conditions and displayed digitally. After the overhaul, new engine and heater hoses, factory radiator, thermostat, radiator cap, fan clutch overhaul, water pump and factory long life coolant, the engine rarely gets to 80 deg (top hose) and 65 deg (bottom hose) even in hot conditions towing a 3300 kg caravan. In cooler temps with no van its about 74 top and about 58 bottom, indicated on the Watchdog. Between about 60 and 80 deg on the top hose the factory gauge is lucky to move a needle width in the centre of the instrument. Where between say 30 and 60 it moves from cold to midrange on the gauge. Remember it is measuring coolant temp NOT block temp and is “restricted” in this mid range electronically.

    Aiden you are totally correct about the hoses. In the kit I purchased there was 4 small shaped hoses which were difficult to change in my workshop which I had never noticed on the engine. They would of been almost impossible to change on the side of the road, as it required considerable disassembly of the engine to even see where they were fitted! They actually supplied coolant to and from the turbo. Mine at 300K were hard and brittle and if they had failed in the middle of whoop whoop they would of dumped the coolant in minutes under the elevated pressure. Don’t forget to change the hoses that feed the heater in your vehicle as the result could be the same?

    Anyway I hope this helps someone, and I am not an agent for Engine Watchdog, however I did speak to the owner seeking advice prior to purchase, and during the conversation he informed a majority of his customers are people who for various reasons had fried their engine!!

    Oh and be cautious testing new thermostats in boiling water prior to fitment as it is possible to damage them, or so I have read. I personally would not do it, however I did purchase a factory thermostat. I did test the old one I removed and it opened about 3 mm at 100 deg C boiling water, when it should of been fully open (about 10mm) at about 90 deg C.

    Regards Russ

  2. Yep I agree stray current is the first thing any aftermarket rad specialist will want checked, maybe even documented to keep warranty on a new replacement radiator.
    I’ve replaced a few in different cars over the yes and it was part of the install process.

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