Sparesbox Blog

When should you replace your radiator?

By Linda Quan

Tue Oct 08 2019

The first sign that you’ll need to replace your radiator is often a puddle of coolant beneath your car. The second sign is if your engine begins to overheat (however, there’s a 50/50 chance that it could also be an issue with your thermostat).

Either way, both mean you have a faulty radiator on your hands and the last thing you want is to be broken down on the side of the road with steam coming out from under the bonnet. A good way to know for sure if your radiator is in trouble is to check your coolant levels every two weeks; if it drops below the minimum mark much faster than usual, you’ve got a radiator leak – the most common cause of a faulty radiator.

The main job of a radiator is to work with the thermostat to keep the engine at operational temperature. Driving when your engine is overheated can lead to a whole range of issues including warped cylinder heads, a blown head gasket and melted engine components, all of which can be very expensive to fix.  


Common Causes of Radiator Problems

Rust in the radiator

The usual cause of an engine leak is corrosion of the radiator due to the presence of air. When the coolant cools down, it decreases in volume and creates an air pocket. An overflow tank should hold enough coolant to fill up the air pocket but a cracked radiator overflow tank (a less common problem if you have aluminium overflow tanks) will let air into the cooling system, causing it to corrode.  

Faulty thermostat

The thermostat is a device which controls the flow of coolant to the radiator. When the engine is cold, the thermostat keeps the main valve closed, blocking the coolant from entering the radiator. Once the engine warms up, the thermostat opens up to allow coolant to flow through the radiator so it can begin to disperse heat. A broken thermostat can keep the main valve closed and accumulate coolant in the radiator until the built-up pressure causes it to crack. 

Damaged radiator fins and tubes

Radiator fins are designed to increase the surface area of the radiator to help it cool faster. Their thinness means they are rather fragile and are easily deformed by stray gravel pieces making their way past the grille or by rough installation and cleaning.

Damage to a large number of fins will block air flow which means the radiator won’t work the way it should. If you’re really unlucky, a rock to the radiator could puncture the core tubes that hold the coolant – when that happens, your radiator will need replacing as soon as possible.   

Sludge build-up

Like the engine, your radiator is susceptible to sludge. Sludge can come from rust deposits, coolant contaminated with transmission fluid, mixing coolants containing incompatible additives, or a cracked cylinder head or blown gasket letting engine oil into the coolant.

Sludge in the coolant thickens it up and can cause clogs in the pipes – if a radiator flush isn’t performed, the radiator sludge build-up will eventually cause a blockage, leading to overheating. 

Cold weather

Extreme cold can freeze your coolant, causing it to expand – this is because frozen coolant takes up more volume than liquid coolant. Too much expansion will crack your radiator.


So... your radiator isn't working. What next?

Some of these issues, such as a broken thermostat or sludge build-up, can be remedied if caught early on. However, if the damage to your radiator is already done, you’ll have no choice but to replace the radiator as soon as possible to avoid racking up costs from further damage.

Small radiator leaks can be fixed temporarily with a radiator stop leak sealant – luckily, at Sparesbox, we stock some of the best radiator stop leaks Australia has to offer including brands like Nulon, Rislone, Castrol and Penrite. Keep in mind, however, that radiator stop leaks are only a temporary solution and you will need to replace your radiator eventually.

Need to replace your radiator?

As daunting as it sounds, replacing your radiator doesn’t have to be difficult – doing it yourself can even save you thousands at the mechanic. At Sparesbox, we stock thousands of products from a great range of popular radiator brands including FloKool, PWR and Mishimoto; our headache-free fitment tool will help you find the right radiator for your vehicle so you can get right into the nuts and bolts.

Sometimes, your radiator is fine and it’s the other parts that need replacing. If you’re looking for thermostats and gaskets, you can check out our extensive Gates, Tridon and Dayco ranges on the website. Otherwise, if you’re looking to replace your radiator hoses, take a look through our Mackay range. Whatever you need, Sparesbox has you covered!