AUSTRALIAN EARTHMOVING57Engines in earthmoving machinery are (almost always) cooled by
a liquid coolant, circulated by a pump through a radiator which
is then then cooled by ambient air moved by a fan. Incorrect
cooling system maintenance can not only lead to overheating
causing piston seizures, cylinder head cracking and head gasket
failures, but also overcooling leading to excessive wear and oil
consumption. Understanding how the cooling system works and
how to maintain it can help to reduce the owning and operating
costs of a machine.In very broad terms, of the heat generated by the fuel burnt in
a typical diesel engine, approximately 1/3 is turned into useable
horsepower, 1/3 goes out of the exhaust and the remaining third
has to be dissipated through the cooling system. In mobile plant
however, the cooling system doesn’t benefit from the ram-air
effect enjoyed by on-road vehicles and can also have to cope
with additional heat from aftercoolers, transmission oil coolers,
hydraulic oil coolers and air-conditioning condensers. That can be
a pretty big ask in the middle of a 40 degree Summer. So what
are the main components making it all happen?
The Coolant. A vital part of the system, not only carrying heat
away from the engine but designed to have a high boiling point, a
low freezing point and anti-corrosion properties.
The Radiator. Takes the hot coolant and flows it through many
tubes, giving it a large surface area so the heat can be taken
away by the air flow. Conventional radiators flow from top to
bottom. Some are cross-flow design, and some are designed to
flow in the bottom, over the top and back down to the bottom
again like an inverted “U”. The radiator cap is designed to keep
the system under a small amount of pressure in order to raise the
boiling point of the coolant. Incidentally, this is why it’s dangerous
to remove the radiator cap when it’s hot. If the coolant happens
to be at a temperature above its boiling point at atmospheric
pressure, suddenly lowering the pressure in the system by
removing the cap can cause the coolant to instantly vaporise.
AUTHOR: CHRIS TAYLOR
cooling
systems.