INTRODUCTION TO THE HMMWV - OD1615 - LESSON 1/TASK 2
The radiator is mounted at an approximate angle of 45 to accommodate the
low silhouette of the vehicle. The radiator holds six gallons of coolant,
while the surge tank holds half a gallon. The radiator shroud channels the
air flow between the radiator and fan for more efficient operation. The fan
is mounted on the fan drive clutch which activates the fan when the coolant
temperature reaches approximately 200 F.
Normally, a 50-50 mixture of
water and ethylene glycol base anti-freeze should be used in the cooling
system. This is to prevent freezing and to protect the metal components.
A separate oil cooler is mounted in front of the radiator. This cooler is
divided into two parts. The top half is for transmission and transfer case
oil; the bottom half is for engine oil.
When the cooling system pressure reaches approximately 15 psi, a valve in
the surge tank cap opens and allows excess pressure to escape into the
Another valve opens at approximately two inches of mercury
a. Purpose of the Lubrication System.
The lubrication system in an
automotive engine supplies a constant supply of oil to all moving parts.
This constant supply of fresh oil is important to minimize wear, to flush
bearing surfaces, and to remove the localized heat that develops between
moving parts as a result of friction. In addition, the oil that is supplied
to the cylinder walls helps the piston rings make a good seal, reducing
(1) Oil as a Lubricant.
The primary function of engine oil is to
reduce friction between moving parts (lubricate). Friction, in addition to
wasting engine power, creates destructive heat and rapid wear of parts. The
greater the friction, the greater the energy needed to overcome that
The increase in energy adds to the amount of heat generated,
causing moving parts that are deprived of oil to melt, fuse, and seize after
The effectiveness of a modern
lubrication system makes possible the use of friction-type bearings in an
engine. Friction between the pistons and the