Pontiac Fiero 1988 Service Manual page 352

ENGINE COOLING 6B-3
CAUTION: If a fan blade is bent o r dam-
aged in any w a y , no-attempt should be
made to repair and reuse the damaged
part. A bent or damaged fan assembly
should always be replaced with a new
fan assembly. It is essential that fan
assemblies remain in proper balance
and proper balance cannot be assured
once a fan assembly has been bent or
damaged. A fan assembly that is not in
proper balance could fail and fly apart
during s u b s e q u e n t u s e , creating an
• extremely dangerous condition.
The majority of non-A/C cars use a fan with
four blades which are unevenly spaced and have
curled tips to provide minimum noise. A fan shroud is
used to prevent recirculation of air around the fan on
most cars.
1 - F L A N G E SEAL
2 - F L A N G E
3 - P8STON
4 -
NUT
5 - V A L V E S E A T
6 - T E F L O N S E A L
7 - V A L V E
8 - RUBBER DIAPHRAGM
9 - WAX P E L L E T
10- COIL SPRING
11— F R A M E
G20007-6B
Figure 3 Pellet Type Thermostat
Temperature Switch
This switch activates a warning lamp in the
instrument cluster if the engine overheats. With
optional instrumentation, a temperature gage replaces
the warning lamp and the temperature switch is
replaced with a transducer. See Section 8A for Tem-
perature Switch location and diagnosis.
Coolant Temperature Fan Switch
This switch regulates voltage to the coolant fan
relay, which operates the fan whenever the engine
coolant temperature exceeds 230°F (110°C). For loca-
tion and diagnosis see Section 8A for Coolant Tem-
perature Fan Switch.
Coolant Recovery System
A recovery-type cooling system is standard on
all cars and is designed to maintain the engine at
proper operating temperatures. The recovery tank col-
lects coolant that expands with rising temperature and
would otherwise overflow from the system. When the
system temperature drops, the coolant is drawn from
the recovery tank back into the radiator by the suction
created by coolant contraction. The cooling system
has been filled at the factory with a high-quality,
inhibited, year-around coolant that meets the stan-
dards of General Motors Specification 1825-M. This
coolant solution provides freezing protection to at
least -37°C (-34°F). It has been formulated to be
used for two full calendar years or 30,000 miles,
whichever first occurs, of normal operation without
replacement, provided the proper concentration of
coolant is maintained.
1 hermostat
A pellet-type thermostat is used in the coolant
outlet passage to control the flow of engine coolant, to
provide fast engine warm-up and to regulate coolant
temperatures. A wax pellet element in the thermostat
expands when heated and contracts when cooled. The
pellet element is connected through a piston to a
valve. When the pellet element is heated, pressure is
exerted against a rubber diaphragm which forces the
valve to open. As the pellet element is cooled, the
contraction allows a spring to close the valve. Thus,
the valve remains closed while the coolant is cold,
preventing circulation of coolant through the radiator.
At this point, coolant is allowed to circulate only
throughout the engine to warm it quickly and evenly.
As the engine warms, the pellet element
expands and the thermostat valve opens, permitting
coolant to flow through the radiator, where heat is
dissipated through the radiator walls. This opening
and closing of the thermostat permits enough coolant
to enter the radiator to keep the engine within operat-
ing limits.
DIAGNOSIS
The following diagnostic information covers
common problems and possible causes. When the
proper diagnosis is made the problem should be cor-
rected by part replacement, adjustment, or repair as
required. Refer to the appropriate section of the ser-
vice manual for these procedures.
SERVICE PROCEDURES
Cooling System Care
The radiator cap should not be removed to check
coolant level. Check the coolant level visually in the
"see-through" coolant recovery tank every time hood
is up. Level should be near "ADD" mark when the
system is cold. At normal operating temperature the
coolant level should increase to the "FULL" mark on
the recovery tank. Coolant should be added only to
the reservoir to raise level to the "FULL" mark. Use a
50/50 mixture of high-quality ethylene glycol anti-
freeze and water for coolant additions. -