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ATV Cooling Systems
- Article submitted by: Ccrane
May 7, 2006
ATV's incorporate some of the most efficient cooling systems of any engine currently in use, but even the most efficient gasoline engines on the planet convert the majority of the chemical energy in the gasoline (more than 50%) into heat.... Not mechanical power.
The bulk of that heat goes right out the exhaust pipe, but some of it soaks into the engine. And so it becomes the job of the engine cooling system to dispose of that heat... and not do harm to the engine.
Air cooled engines:
Most ATV's incorporate air-cooled engines, which feature cooling fins on the cylinder and head to conduct heat out of the engine and radiate it to the atmosphere. In addition to these fins, most engines have strategically located oil passageways and oil jets that serve a cooling function while simultaneously lubricating the engine.
Some engines hold more oil than others to help disperse engine heat, and a number of ATV's also feature oil coolers, which serve as small radiators to cool the engine... More on radiators is soon to come.
Liquid cooled engines:
In a liquid cooled engine fluid circulates through passageways in the engine, absorbing heat and cooling the engine. After the fluid leaves the engine, it passes through a radiator... which transfers the heat from the liquid to the atmosphere through a system of fins and tubes.
Because of varying climates and conditions on earth, varying from well below freezing (32 degrees F.) to well over 100 degrees F.... whatever fluid is used to cool an engine must offer a very low freezing point and a high boiling point... while also carrying a 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 cold conditions. Therefore, most liquid cooled engines use a mixture of water and ethylene glycol, also known as anti-freeze. By adding anti-freeze to water (distilled preferably, as tap water may cause corrosion), the boiling and freezing points improve drastically.
For example: Compared to plain water, a recommended 50/50 blend of anti-freeze and water shifts the boiling point from 212 degrees F. to 228 degrees F., and the freezing point from 32 degrees F. to -35 degrees F.
Engine cooling systems also use 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 when you pressurize the system.
Most systems use a pressure limit of around 15 PSI. which raises the boiling point another 40 degrees F. so the coolant can handle higher temperatures.
Because the cooling system is pressurized when the engine is hot, removing the radiator cap on your machine can allow coolant to spray out, causing SERIOUS BURNS .
ALWAYS allow the engine and radiator time to cool completely before removing the radiator cap. When topping off the system, always add coolant to the reserve tank. The radiator cap only needs to be removed when draining or refilling the entire cooling system. Avoid spilling coolant on painted surfaces, and because anti-freeze is toxic... keep it away from eyes, mouth, skin, clothes, and out of reach of children and pets. Always dispose of old anti-freeze properly.
Engine coolant, as with the engine oil... should be checked regularly to maintain proper levels and should be replaced at intervals suggested by the manufacturer. Dispose of oil and coolant properly. Hoses that connect the engine and radiator should also be checked regularly for signs of wear... (i.e. cracks, melting spots, swelled areas, coolant residue).
The radiator cap is a vital part of the coolant system, it maintains pressure, as the coolant heats up. If the pressure exceeds the prescribed limit, the pressure valve opens and coolant can then flow into the reserve tank until it's needed again.
The reserve tank temporarily stores the surplus volume of heated coolant as needed. Coolant can flow back into the system as a hot engine cools down.
As coolant passes through the tubes of a radiator, the fins between the tubes dissipate heat into the air. Radiator fins that are crushed or twisted will also decrease the flow of cooling air into the radiator, carefully straighten damaged fins using a small flat-blade screwdriver. (A radiator with 1/3 or more of it's fins crushed or twisted can destroy an engine).
Whether your ATV relies on engine fins and an oil cooler, or a radiator and anti-freeze for cooling.... these systems depend on a steady flow of air to keep the engine cool. So NEVER let mud accumulate and clog things up. (Always wash radiators from back to front... washing front to back could drive debris and mud deeper into the radiator).
Many mud-riding ATV enthusiasts have opted to relocate their radiators to the front rack of the machine... thus preventing it from being submerged or subjected to mud. There are many after-market products to increase the efficiency of your cooling systems currently on the market (i.e. Radiator re-locating kits, after-market radiators with increased capacity or more open air-flow, heat-wrap kits to help insulate the exhaust system and keep heat where it's supposed to be... and coolant additives to increase anti-freeze efficiency in high-heat conditions)
mnyman's Rancher
