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Repairing and Replacing Classic Car Radiators: The Ultimate Guide

Posted on: 05 Nov 2021

Home | General | Repairing and Replacing Classic Car Radiators: The Ultimate Guide

A working radiator is an essential component if you want your classic car to be roadworthy. In any car, the radiator is the only thing keeping the engine from overheating and causing permanent, irreversible damage to the engine while driving, including possible warping and deformation of the cylinders and pistons. In an old classic car, a blown engine can end up costing you more than the car is worth.

As specialists in the sale of brand new and custom-built classic motor car radiators, we’ve compiled everything you need to know about the causes of a broken car radiator, how to spot the signs that your radiator may be failing and steps you can take to prevent your radiator from breaking down in the future.

What causes a car radiator to fail?

A car radiator uses heat transfer to dissipate heat from the liquid flowing through the car’s engine into the atmosphere. The liquid used is a special radiator coolant (a precise mix of water and antifreeze for your car), which circulates around the metal and absorbs heat from the engine. The coolant will then pass through thin pipes in the radiator which are exposed to air through the fins, conducting the heat from the tubes into the air flowing through the radiator. Fans are also commonly used to circulate air through the radiator and speed up the cooling process.

A car radiator will fail when a part of it is broken, cracked or clogged and cannot perform it’s cooling capacity as efficiently as usual. This could be due to a variety of factors, including:


The most common cause of problems within the radiator is corrosion. The seams on the radiator’s side tanks start to break down as the metal corrodes, causing leaks and rusting throughout the cooling system. Corrosion within a car radiator system is typically caused by the coolant having an incorrect antifreeze-to-water concentration, or if there is no additive present in the water at all.

Lack of maintenance

This can include routine cleaning and flushing the engine coolant on a regular basis. If the fluid isn’t changed regularly it can become acidic and will form deposits on the inside of the radiator. A lack of cleaning can lead to a progressive build-up of these deposits throughout the radiator, resulting in the radiator becoming clogged as the internal deposit build-up blocks the flow of the coolant around the engine.

Seal Leaks

Caused by the seal between two gaskets drying out or swelling, seal leaks can reduce the amount of coolant in the radiator and cause overheating and an excess of smoke. If the source of the leak is a leaking head gasket, the pressure in the combustion chamber will drop, causing the classic car radiators to crack.

Physical Damage

Caused by dust, dirt and debris impacting the radiator through the grille. This damage can lead to leaks and debris getting stuck in the radiator. The lack of fluid combined with the clogging of the cooling system prevents the correct amount of coolant from circulating through the engine, causing it to overheat.

How do you know if your car needs a new radiator or repair?

It’s critical to resolve any major radiator issues as soon as possible. These are the tell-tale signs of a broken or faulty radiator you should keep an eye out for to avoid any further damage to your vehicle.


Overheating is the most common symptom of a failing radiator because it indicates that coolant is not flowing properly through the radiator and that the radiator is not doing its job of keeping your engine cool. First, check your dashboard, if your temperature warning light comes on or if the needle on your temperature gauge is significantly higher than usual, it may be a sign your engine is overheating.


Examine the radiator’s exterior for signs of corrosion. The odd rusty water stain may not indicate any real damage, but excessive rust on the exterior may indicate irreversible damage to the radiator’s core. If the metal is flaking or chipped, and you are unable to remove the fittings due to excessive oxidisation, it is time to replace your radiator.

Leaking Coolant

Leaking coolant is a major indicator of a broken or cracked radiator. The hoses and hose connections collect sediment and rust overtime which can damage the material and create holes, resulting in small drops of coolant leaking out of the radiator where the car is parked. Depending on where the leak is coming from, you may only require a simple part replacement.


Another sign that something is wrong with the vehicle is smoke coming from the engine. The engine will burn the coolant that is leaking and emit smoke from under the front hood. If smoke is coming from the tailpipe, it indicates that the head gasket has been damaged.

Fluid Discolouring

Vehicle coolant should be brightly coloured, often green, yellow or orange, however internal deposits and sludge can contaminate the coolant, turning it into a more rusty colour, or in extreme cases the colour of oil. Take a look in the coolant overflow tank in your vehicle to determine the condition of your coolant.

Broken Fins

If the fins on the radiator are broken or damaged, the airflow to the coolant may be blocked, resulting in the coolant in the tubes being unable to effectively cool down before it flows back into the engine. This can cause your vehicle to overheat, and can also occur when the fins are blocked by any sediment or debris.

How do you maintain a car radiator to prevent damage and leaks?

Preventing your classic car radiator from breaking down at the start can save you a lot of money down the line. These are our top tips for maintaining your radiator to ensure it stays more efficient for longer!

Regular Radiator Flushes

Regularly flushing your radiator prevents coolant from becoming acidic, as well as removing rust, contaminants and scale deposits which can build up in the cooling system overtime. If a radiator flush is not carried out regularly, rust will continue to form and cause corrosion to the radiator tank, which is why we recommend getting your radiator flushed every 12 months.

Keep Coolant Filled

Keeping the amount of coolant full at all times ensures there is enough fluid in the radiator to effectively cool down the engine. You can check the levels of coolant in your vehicle by carrying out a fluid check. If you’re topping it up, make sure you choose a high quality coolant to prevent rust and corrosion, don’t mix coolants and only use coolants suitable for your specific make and model of car, as using the wrong kind of antifreeze may void the manufacturer’s warranty on your cooling system.

Keep Your Radiator Clean

You can get your radiator cleaned whenever you go for a tire rotation or oil change. This can remove any deposits in the cooling system and clear any build-up of sediment between the fins which may be restricting the airflow to the coolant, a simple solution that can save you a lot of extra hassle later on.

Regularly Check Hoses

See if any of the radiator’s coolant hoses are leaking or need changing. Corrosion and other general wear and tear can cause small splits and cracks in the tubing, which can have a big impact on the performance of your radiator if gone unnoticed.

Don’t Overload Your Vehicle

Keep to the maximum load of your vehicle as listed in the owner’s manual. Overloading adds extra unnecessary stress to the engine and means the radiator needs to work faster to maintain a cool temperature, increasing the risk of engine failure from overheating.

Our range of classic car radiator services 

Coolex are experts at providing specialist classic motor cooling products and a range of maintenance and breakdown services to classic car owners across the world. Whether you have a faulty radiator that needs repairing or want to buy a new, custom-built radiator for your vehicle we deliver exceptional service to all of our customers.
For repairs, replacement parts, the recore of an existing engine or to buy a brand-new off the shelf classic car radiator, Coolex are the best specialist motor cooling company for you. Browse our range of services or view our catalogue of products online today!