The Workings of Holden Cooling Systems Explained

20 Mar

holden cooling system

A typical Holden 4 cylinder engine cruising on the highway at around 80 km/h will produce around 4.000 controlled explosions a minute inside the engine. Obviously, with these explosions comes a great amount of heat, which if not controlled will completely destroy the engine in a few minutes. And that’s where cooling systems come into play. Cooling systems have remained almost the same since the 20s. And while they’ve become infinitely more efficient and reliable at doing their job, they still consist of liquid coolants circulating through the engine, then to the radiator where they’re cooled by the air stream entering through the Holden’s front grille.

So how do these Holden car parts work? Well, before I get into the workings of cooling systems, worth noting is that there are two types – liquid and air cooled. Most modern cars use a liquid cooled system, which is made up of a water pump to circulate the liquid coolant, passages inside the engine heads and block, thermostat to control the coolant’s temperature, a radiator to cool the liquid coolant, a radiator cap to control the pressure inside the system and hoses to transfer the liquid coolant from the engine to the radiator.

holden cooling system

Cooling systems work by releasing a liquid coolant via passages in the engine heads and block. As the coolant flows through, it picks up heat from the engine, and the heated fluid is then sent through a rubber hose to the cooling radiator, where it’s cooled by the air stream entering from the grill. Once the liquid is cooled, it goes back to the engine to absorb some more heat. Then, the water pump keeps the fluid moving through the system’s plumbing and hidden passages.

Further, there’s a thermostat between the radiator and engine to ensure the coolant is kept above a specific preset temperature. If the coolant temperature drops below the preset temperature, the thermostat will block the flow to the radiator, forcing the coolant to instead go back to the engine. The coolant will keep on circulating like this until it reaches the specified temperature, and only then will the thermostat open the valve which allows the coolant to go back to the radiator.


The cooling system is also designed to be pressurised in order to prevent the liquid coolant from boiling. When under pressure, the coolant’s boiling point is raised significantly. However, if too much pressure is applied, the hoses and other coolant Holden car parts can burst, so the system will also need something to relieve pressure if it gets to a certain point. And this is where the radiator cap comes into play.

Radiator caps are designed to release pressure if it reaches a predetermined upper limit that the system is designed to handle. Up until the 70s, the cap would release the extra pressure to the pavement, but nowadays, cooling systems can capture the released fluid and store it temporarily in a special reserve tank, which is then released to the cooling system after the engine has cooled down.

Maintaining your cooling system is important, as an overheating engine will quickly self-destruct. The most important part of maintaining one is flushing and refilling the coolant. This is due to the fact that antifreeze features additives that are designed to prevent corrosion, which tends to accelerate when several different types of metal interact with one another, causing the build up of scale that clogs the thin flat tubes in the heater core and radiator.

mechanic fixing car

The anti-corrosion additives in the antifreeze prevent this from happening, but they do have a limited lifespan. Newer antifreeze will last for 5 years or about 200.000km before it needs to be replaced. Extended life antifreeze is typically red in colour, whereas standard antifreeze used in vehicles is green in colour and should be replaced every 2 years or 50.000km. While you can replace standard antifreeze with an extended life one, you’ll have to completely flush the standard one.

With that said, look for a mechanic to do it for you, as this requires the removal of the thermostat and special equipment to be done properly. Professional flushing is especially important if your coolant has debris floating in it or looks brownish. When removing the thermostat for flushing, replace the thermostat as well for the appropriate temperature, just for affordable insurance.

Performing preventative cooling system maintenance once every two years is highly recommended, and it should consist of a visual inspection of the system’s components, including hoses and belts, a radiator pressure cap test, a thermostat check for proper closing and opening, an internal leak test for combustion gas leakage, an engine fan test, a pressure test to find external leaks to the system’s parts (including the water pump, radiator, engine coolant passages, heater core, radiator and heater hoses), and a system power flush and refill.

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