Cooling Systems
Radiator failure information
  • Cooling Systems

    Although gasoline engines have improved a lot, they are still not very efficient at turning chemical energy into mechanical power. Most of the energy in the gasoline (perhaps 70%) is converted into heat, and it is the job of the cooling system to take care of that heat. In fact, the cooling system on a car driving down the freeway dissipates enough heat to heat two average-sized houses! The primary job of the cooling system is to keep the engine from overheating by transferring this heat to the air, but the cooling system also has several other important jobs.
    The engine in your car runs best at a fairly high temperature. When the engine is cold, components wear out faster, and the engine is less efficient and emits more pollution. So another important job of the cooling system is to allow the engine to heat up as quickly as possible, and then to keep the engine at a constant temperature.
    In this article, we'll learn about the parts of a car cooling system and how they work. First, let's look at some basics.

    The Basics

    Inside your car's engine, fuel is constantly burning. A lot of the heat from this combustion goes right out the exhaust system, but some of it soaks into the engine, heating it up. The engine runs best when its coolant is about 200 degrees Fahrenheit (93 degrees Celsius). At this temperature:

    • The combustion chamber is hot enough to completely vaporize the fuel, providing better combustion and reducing emissions.
    • The oil used to lubricate the engine has a lower viscosity (it is thinner), so the engine parts move more freely and the engine wastes less power moving its own components around.
    • Metal parts wear less.

    There are two types of cooling systems found on cars: liquid-cooled and air-cooled.

    Liquid Cooling

    The cooling system on liquid-cooled cars circulates a fluid through pipes and passageways in the engine. As this liquid passes through the hot engine it absorbs heat, cooling the engine. After the fluid leaves the engine, it passes through a heat exchanger, or radiator, which transfers the heat from the fluid to the air blowing through the exchanger.

    Air Cooling

    Some older cars, and very few modern cars, are air-cooled. Instead of circulating fluid through the engine, the engine block is covered in aluminium fins that conduct the heat away from the cylinder. A powerful fan forces air over these fins, which cools the engine by transferring the heat to the air.

    Since most cars are liquid-cooled, we will focus on that system in this article.


    The cooling system in your car has a lot of plumbing. We'll start at the pump and work our way through the system, and in the next sections we'll talk about each part of the system in more detail.

    The pump sends the fluid into the engine block, where it makes its way through passages in the engine around the cylinders. Then it returns through the cylinder head of the engine. The thermostat is located where the fluid leaves the engine. The plumbing around the thermostat sends the fluid back to the pump directly if the thermostat is closed. If it is open, the fluid goes through the radiator first and then back to the pump.

    There is also a separate circuit for the heating system. This circuit takes fluid from the cylinder head and passes it through a heater core and then back to the pump.

    On cars with automatic transmissions, there is normally also a separate circuit for cooling the transmission fluid built into the radiator. The oil from the transmission is pumped by the transmission through a second heat exchanger inside the radiator.


    Cars operate in a wide variety of temperatures, from well below freezing to well over 100 F (38 C). So whatever fluid is used to cool the engine has to have a very low freezing point, a high boiling point, and it has to have the capacity to hold a lot of heat.

    Water is one of the most effective fluids for holding heat, but water freezes at too high a temperature to be used in car engines. The fluid that most cars use is a mixture of water and ethylene glycol (C2H6O2), also known as antifreeze. By adding ethylene glycol to water, the boiling and freezing points are improved significantly.

    Fluid - Freezing Point - Boiling Point

    Pure Water: 0 C / 32 F - 100 C / 212 F

    50/50 mix of C2H6O2/Water: -37 C / -35 F - 106 C / 223 F

    70/30 mix of C2H6O2/Water: -55 C / -67 F - 113 C / 235 F

    The temperature of the coolant can sometimes reach 250 to 275 F (121 to 135 C). Even with ethylene glycol added, these temperatures would boil the coolant, so something additional must be done to raise its boiling point.

    The cooling system uses pressure to further raise the boiling point of the coolant. Just as the boiling temperature of water is higher in a pressure cooker, the boiling temperature of coolant is higher if you pressurize the system. Most cars have a pressure limit of 14 to 15 pounds per square inch (psi), which raises the boiling point another 45 F (25 C) so the coolant can withstand the high temperatures.

    Antifreeze also contains additives to resist corrosion.

    Water Pump

    The water pump is a simple centrifugal pump driven by a belt connected to the crankshaft of the engine. The pump circulates fluid whenever the engine is running.

    The water pump uses centrifugal force to send fluid to the outside while it spins, causing fluid to be drawn from the centre continuously. The inlet to the pump is located near the centre so that fluid returning from the radiator hits the pump vanes. The pump vanes fling the fluid to the outside of the pump, where it can enter the engine.

    The fluid leaving the pump flows first through the engine block and cylinder head, then into the radiator and finally back to the pump.


    The engine block and cylinder head have many passageways cast or machined in them to allow for fluid flow. These passageways direct the coolant to the most critical areas of the engine.

    Temperatures in the combustion chamber of the engine can reach 4,500 F (2,500 C), so cooling the area around the cylinders is critical. Areas around the exhaust valves are especially crucial, and almost all of the space inside the cylinder head around the valves that is not needed for structure is filled with coolant. If the engine goes without cooling for very long, it can seize. When this happens, the metal has actually gotten hot enough for the piston to weld itself to the cylinder. This usually means the complete destruction of the engine.

    One interesting way to reduce the demands on the cooling system is to reduce the amount of heat that is transferred from the combustion chamber to the metal parts of the engine. Some engines do this by coating the inside of the top of the cylinder head with a thin layer of ceramic. Ceramic is a poor conductor of heat, so less heat is conducted through to the metal and more passes out of the exhaust.


    A radiator is a type of heat exchanger. It is designed to transfer heat from the hot coolant that flows through it to the air blown through it by the fan.

    Most modern cars use aluminium radiators. These radiators are made by brazing thin aluminium fins to flattened aluminium tubes. The coolant flows from the inlet to the outlet through many tubes mounted in a parallel arrangement. The fins conduct the heat from the tubes and transfer it to the air flowing through the radiator.

    Radiators usually have a tank on each side, and inside the tank is a transmission cooler. In the picture above, you can see the inlet and outlet where the oil from the transmission enters the cooler. The transmission cooler is like a radiator within a radiator, except instead of exchanging heat with the air, the oil exchanges heat with the coolant in the radiator.

    Pressure Cap

    The radiator cap actually increases the boiling point of your coolant by about 45 F (25 C). How does this simple cap do this? The same way a pressure cooker increases the boiling temperature of water. The cap is actually a pressure release valve, and on cars it is usually set to 15 psi. The boiling point of water increases when the water is placed under pressure.

    When the fluid in the cooling system heats up, it expands, causing the pressure to build up. The cap is the only place where this pressure can escape, so the setting of the spring on the cap determines the maximum pressure in the cooling system. When the pressure reaches 15 psi, the pressure pushes the valve open, allowing coolant to escape from the cooling system. This coolant flows through the overflow tube into the bottom of the overflow tank. This arrangement keeps air out of the system. When the radiator cools back down, a vacuum is created in the cooling system that pulls open another spring loaded valve, sucking water back in from the bottom of the overflow tank to replace the water that was expelled.


    Like the thermostat, the cooling fan has to be controlled so that it allows the engine to maintain a constant temperature.

    Front-wheel drive cars have electric fans because the engine is usually mounted transversely, meaning the output of the engine points toward the side of the car. The fans are controlled either with a thermostatic switch or by the engine computer, and they turn on when the temperature of the coolant goes above a set point. They turn back off when the temperature drops below that point.

    Rear-wheel drive cars with longitudinal engines usually have engine-driven cooling fans. These fans have a thermostatically controlled viscous clutch. This clutch is positioned at the hub of the fan, in the airflow coming through the radiator. This special viscous clutch is much like the viscous coupling sometimes found in all-wheel drive cars.

    Heating System

    You may have heard the advice that if you car is overheating, open all the windows and run the heater with the fan going at full blast. This is because the heating system is actually a secondary cooling system that mirrors the main cooling system on your car.

    The heater core, which is located in the dashboard of your car, is really a small radiator. The heater fan blows air through the heater core and into the passenger compartment of your car.

    The heater core draws its hot coolant from the cylinder head and returns it to the pump -- so the heater works regardless of whether the thermostat is open or closed.

    For more information on car cooling systems and related topics, check out the links on the next page.

  • Radiator failure information

    Premature radiator failure-/causes.
    Corrosion ¬- Internal and External.
    Erosion - Internal and External.
    Stray Current - Electrolysis Internal- External.
    Mechanical Damage - External

    Stray currents cause premature corrosion failures in radiators, water pumps and thermostat housings as well as premature ageing in coolant hoses. When we say premature, we mean in as little as three weeks.

    Do’s and Don’ts:

    • Never mix different brands of coolants or inhibitors. Mixture of incompatible coolants can induce radiator fouling and can reduce the corrosion protection of the coolant. Always flush out the cold coolant.
    • Never use coolants that foam as this will lead to increased cavitation erosion of the water pump. Shake the bottle of coolant then let it stand for 5 seconds, if the foam has broken and the fluid has returned to normal then it probably won’t foam in the cooling system. If the foam has not broken after 5 seconds then it might pay to find another product.
    • Never under treat a cooling system as the incorrect ratio of coolant can actually increase the corrosion rate to above that of plain water.
    • Only use the best quality water. De-mineralised is the best, never use bore or spring water.
    • Always check for stray electrical current in the cooling system.
    • If the vehicle is within the new vehicle warranty period, always use the manufacturer’s recommended coolant as to do otherwise could void the warranty should the cooling system fail.
    • Always use the service stickers supplied by the coolant manufacturer to avoid any confusion as to which type of coolant is in the system when a top up is required.
    • Always dispose of used coolants correctly. All used coolants will contain heavy metals irrespective of their claims of being environmentally friendly.

    Whilst not wanting to pick on any one area of the automotive industry, our own experience tells us that many vehicles we have examined for electrolysis and chemical corrosion damage are those that have had recent paint and panel repairs. If you suspect that a radiator has failed from electrolysis and you can’t find any apparent reason for it, look for signs of recent repairs (keep in mind that the problems can exist right from the time the vehicle was manufactured)
    If you spot repairs, be wary of earth wires that:

    1. Are not connected.
    2. Are loose, corroded or insecure.
    3. Earth wire mounting points have recently been painted, thus paint may be down the threaded holes causing poor earth contact.
    4. Whist you are monitoring the presence of stray voltage in the cooling system, have a fellow worker operate the brake lights, parking, head and high beam lights and check for any increase in voltage readings in your multimeter
    5. Also, turn on as many accessories as you can to load the vehicle’s electrical system whilst monitoring stray current.
    6. Check battery cables and mid cable securing points for corrosion and tightness.

    Testing for Stray Current:

    Using your multimeter, connect one lead to negative side of battery and then with a test probe immersed in the coolant, make sure it doesn’t touch the core and for a proper reading the probe must stay in the same place in the neck at all times. If a current measuring above 50mv is present you then have to start looking for the source. 
At this point, we have to say that if you have found a problem relative to the stray current, CHANGE THE COOLANT. Unfortunately we have found with some brands of coolant that their chemical composition does not allow them to dissipate the charged oxygen hat has resulted from stray current, so if you are unaware of the coolant in the system, flush it and replace it. 
Common Sources of Stray Current.

Ford Laser: Multi earth plugs located at the front of both chassis rails, Check the thermo fan earth circuit.
    • Ford Falcon: Main battery earth cable fitting at the engine block. Wiring harness fitting at the right front inner guard.
    • Holden Commodore: Main battery earth cable fitting at the engine block. Rear stop light wiring harness earths. Earthing point located behind right front headlight.
    • Nissan Pulsar: Brown coloured earth cables attached to right side rear cylinder head bolt. ECU earth. Earth circuit for thermo fan.
    • Early Hyundai’s: Multi earth wire point located at left front inner guard, cut this off and replace with eyelet connectors.
    • Sigma/Magna: Main battery earth cable (both ends)
    • Nissan Skyline/Pintara: Air conditioning fan earth circuit, change from condenser mounting to adjoining radiator support panel threaded hole.

    Unfortunately, in recent times we are coming across more and more cooling systems and engine failures associated with chemical corrosion. It is a problem common with poor quality inhibitors, low dosages of inhibitor, but we see many where different brands of inhibitors have been mixed and the results are catastrophic.

    The mixing of different brands can degenerate into the formation of a chemical cocktail, which can strip metal away with amazing speed. 
The internals will show a dark Grey or black discolouration. You can also try removing the radiator cap and feeling the top of the core tubes, they will feel flexible, even soft to touch. 
Where this indication is present you may also find items such as thermostat housings and water pumps showing signs of cavitation.

    Where chemical corrosion has occurred, quite often the cooling systems components such as the thermostat housing, water pump, heater and coolant pipes will be badly discoloured. 
Chemical corrosion can also lead to the formation of small hard deposits of metals and rust within the radiator or engine block causing hard to find overheating problems. These deposits can be very hard to shift if they have been building up over a period of time and as such, become firmly lodged in coolant tubes and within water passages, etc. Keep in mind that 1.6mm of corrosion build up on aluminium causes as much heat retardation as 10.4mm of cast iron.

    Mixing of coolants and even poor quality coolants can cause foaming and it’s the introduction of oxygen that leads to the formation of air bubbles that create their own version of cavitation erosion. 
The bubbles or vapours, which result from the chemical activity, continually explode against the engine’s hot spots and if not caught early can completely destroy an engine. The exploding bubbles of air cause a hammering effect on the metal gradually eroding away that area and eventually forming a small pin hole. Often a large piece of metal will simply disappear from within the engine. Cavitation can be particularly harsh on cylinder liners and their seals and at different points of the cylinder head and gasket.

    Stop Press

    Don’t assume that fitting an earth wire directly to the radiator core is a fix all, We did a test on an aluminium core and the wire actually increased the current.

    Stray Current explanation & testing procedure:

    In simple terms stray current is a chemical/electrical process which causes an electrical current to pass through a vehicles cooling system fluid. It can cause rapid damage to radiators and will indirectly cause problems with other engine components such as water pumps, thermostat housings, etc. 
This is brought about when one or more items such as a cooling fan or headlamp develops a problem in its electrical circuitry. This causes an electrical current to seek out an earth path via the radiator core through the engine coolant.


Remove the radiator cap and run the engine to operating temperature. Do not rev the engine as this may cause the coolant to aerate. Note: Removing the cap will reduce the boiling point of the coolant. This may result in electric cooling fans not operating on some vehicles,
    • Switch ON all electrical items including Items such as a mobile phone, rear demister, driving lights, etc.
    • Switch an analogue multi-meter to a scale of 5 volts DC or less. Ideally the meter should be capable of reading millivolts. Do not use a digital multi-meter, as its internal operating characteristics are not suitable for this test.
    • Place the negative lead of the multi-meter on the battery negative post.
    • Dip the positive lead into the coolant without touching the filler neck or the core of the radiator
    • A reading of more than .05 volts indicates the presence of a potentially damaging stray current passing through the coolant. Ideally the voltage should be 0 volts, however it is highly possible that some voltage level will be detected
    • If no voltage or a very low voltage is detected, carry out the same test as in point 4, but with the ignition OFF.
    • If voltage is detected, isolate the circuit by turning all electrical items OFF and switching each circuit ON individually.


    Refilling a cooling system with coolant will itself generate a current that lasts approximately twelve hours. 
This can be avoided by refilling a repaired vehicle, for example, with clean water and then proceeding to test for stray current.

    Cooling System Flushing Procedure:

    Because coolant/inhibitors from different manufactures have different chemical compounds, which may adversely react if mixed, it is important that you DO NOT create a chemical cocktail within your cooling system by mixing different brands of coolant/inhibitor. Even though the coolant has been drained from the system, the inhibitors remain affixed to the cooling system components and must be chemically removed, using a quality alkaline flush.


    1. Ensure the cooling system is sound and free from leaks and check all components for wear and condition. If need, replace worn components.
    2. Choose a quality alkaline cooling system flush (500mL. Per 12 Litres). Observe the instructions on the container.
    3. Replace the radiator cap and run the engine at operating temperature for 15 minutes in 4 cylinder vehicles and 30 minutes in 6 or 8 cylinder vehicles. (Ensure the vehicle heater is turned on).
    4. Drain and rinse the cooling system including the overflow bottle and heater core. At this point a power flushing machine may be used if this equipment is available.
Rinse the system with clean water until you are convinced that the only fluid remaining in the system is clean water- RINSE- RINSE- RINSE (this may need to be refilled and drained a number of times).
    2. Refill the cooling system using clean water (demineralised or distilled water), to perform a stray current check.
    3. Do not add coolant at this time until a complete stray current check has been performed (refer to stray current procedure). The presence of stray current will deteriorate the cooling fluid quality immediately. 
Always ensure you select a coolant/inhibitor that meets the vehicle manufacturer’s recommendation or one that meets AS 2108-97 Type A or Type B whichever is recommended as being in support of the vehicles manufacturers recommended coolant performance standard.
    4. Ensure the correct rates of coolant/inhibitor is used, as overdosing or under-dosing will have a direct affect on the performance of the cooling system and the life of the components including the radiator.
    5. Only after the vehicle has been cleared of the possibility of stray current (electrolysis). Rebuild the cooling fluids by first adding the selected product then topping up with clean water (demineralised or distilled water). NOTE: NEVER MIX TWO BRANDS OF COOLANT!
    6. Mix a portion of the coolant for the owner to use for topping up coolant level.

    Dispose of Waste Fluid Correctly.

  • Support

    Thank you for choosing a radiator from the Fenix commuter series. We trust that this radiator will be of the same or better quality as your original radiator.
Fenix radiators come with a comprehensive limited warranty and are designed and manufactured to the highest of standards. At Fenix we greatly care for quality. Each Fenix radiator is made and rigorously tested at some of the world’s best radiator manufacturing facilities. We take pride in our radiators and you can too.

    Important Installation Instructions

    All FENIX radiators should be installed in the correct manner according to the cars manufacturer.

    However please note:

    • Test for stray currents in the engine with a volt meter, to eliminate any chance of electrolysis which can corrode engine parts including the new radiator.
    • Flush cooling system with flushing agent, so as to make sure there will be no contamination with the new anti-freeze. Contamination can corrode your new radiator as well, so this is important.
    • After installation please check all plugs are tight and sealed, and also a visual check to make sure all is working correctly.
    • Use appropriate anti-freeze and correct levels of antifreeze/water mix or premixed anti-freeze. Please note DO NOT mix two types of anti-freeze together as there will be a high chance of contamination which will erode your radiator.
    • Features

      • High temperature resistant
      • High compression resistant
      • High heat exchange efficiency
      • Heat resistant materials
      • Machine made and tested
      • Stronger and lighter

      Important installation instructions

      All FENIX radiators should be installed in the correct manner according to the cars manufacturer.

      Important Installation Instruction

      1. Test for stray currents in the engine with a volt meter, to eliminate any chance of electrolysis which can corrode engine parts including the new radiator.
      2. Flush cooling system with flushing agent, so as to make sure there will be no contamination with the new anti-freeze. Contamination can corrode your new radiator as well, so this is important.
      3. After installation please check all plugs are tight and sealed, and also a visual check to make sure all is working correctly.
      4. Use appropriate anti-freeze and correct levels of antifreeze/water mix or premixed anti-freeze. Please note DO NOT mix two types of anti-freeze together as there will be a high chance of contamination which will erode your radiator.