Excellent condition.

COOLING SYSTEM SERVICE

AIR vs. LIQUID-COOLED

INTRODUCTION

Some engines (usually small and made of aluminum) are

air-cooled by convection; that is, by forcing large quantities

of air over fins on the cylinder head. Design-wise, they

require special care to avoid hot spots, greater internal

clearances and high fan speeds compared to liquid-cooled

engines. Functionally, air-cooled engines tend to have high

noise levels, run at somewhat higher temperatures and

require richer air-fuel mixture at idle speeds... but they

warmup more quickly and the cooling system is relatively

trouble-free. About the only service required is to be sure

that (1) the fan operates at the right speed, (2) the fan drive

belt is properly tensioned, (3) the fan shrouds are in place.

and (4) the fins are cleaned.

Most engines, including all Ford-built engines, are liquid-

cooled because they give more uniform metal temperatures

and cause few noise problems. However, they do require

more service, as detailed in this article.

HISTORY OF IMPROVEMENTS

Henry Ford's first cooling system, way back in 1896, used a

"thermo-siphon" action that depended on a difference in

the density of hot and cool water to achieve circulation. Hot

water flowed from the top of the two-cylinder engine to the

top of a non-finned tank (located under the front seat), and

cool water flowed from the bottom of the tank to the bottom

of the engine. Unfortunately, this design didn't do a very

good job of cooling (nor did it provide much of a "hot

seat), due to boiling and leak problems together with in-

sufficient heat dissipation. Radiators and water pumps

quickly corrected this problem, as the first in a long list of

improvements. Antifreeze and thermostats appeared in the

late 1920's, which eliminated the need to drain the system

and store the car on blocks during the winter. In the late

1940's, pressurized systems significantly reduced boiling

problems and allowed greater under the hood tempera-

RADIATORS

fures associated with larger engines and power-assist ac-

cessories. Scores of other changes have made the modern

cooling system (Fig. 1) a rather sophisticated design to

are regulated by coolant-temperature sensitive devices.

the point where most emission, ignition and fuel systems

COOLANT TEMPERATURE

SENDING UNIT

HEATER

HOSE INLET

HEATER HOSE

OUTLET

RADIATOR

PRESSURE

THERMOSTAT

HOUSING

SPACER

GRILLE

RADIATOR

DRAIN

RADIATOR

BYPASS

FAN

SHROUD

ENGINE

DRAIN

FAN CLUTCH

HYDRAULIC

WATER

PUMP

TRANSMISSION

OIL COOLER

Figure 1-Typical V-8 Cooling System

COMPONENT DESCRIPTION

Ford-built cars and light trucks use two types of radiators;

downflow and crossflow. Downflow radiators use an upper

and lower tank, with the coolant flowing from top to bottom

as it cools. Crossflow radiators (which permit lower hood

designs) have a tank at each side, with the coolant flowing

horizontally as it cools. Most radiators use an overflow tube

to vent coolant in case temperatures and pressures become

excessive. However, some radiators (usually with extra

cooling options) feature an external reservoir (expan-

sion") tank to keep coolant from boiling away under peak

load conditions. Also, cars with an automatic transmission

the transmission fluid.

have a heat exchanger in the bottom, or side, tank to cool

RADIATOR CAP

All Ford cooling systems are "pressurized" to raise the

boiling point of the coolant, which permits higher operating

temperatures. This requires a special cap (Fig. 2) with two

spring loaded valves. One opens if the pressure exceeds a

specified value (see Specifications, Page 14) and the other

when the engine cools and a vacuum is formed. The cap is

located at the top center or side of all radiators, except

1975-76 Mustang II with 302 engine, where it's located on

the upper radiator hose.

VACUUM SEAL

Figure 2-Radiator Pressure Cap

OVERFLOW TUBE

PRESSURE SEAL