Pontiac Fiero 1988 Service Manual page 351

SB-2 ENGINE COOLING
CAUTION: A s long as t h e r e is pressure
in t h e cooling system, t h e t e m p e r a t u r e
can be considerably h i g h e r t h a n t h e
boiling temperature of t h e solution in
t h e radiator without causing t h e solu-
t i o n t o boil. Removal of t h e radiator cap
w h i l e engine is h o t and pressure is high
w i l l cause t h e solution t o boil instanta-
neously a n d p o s s i b l y w i t h explosive
f o r c e , s p e w i n g t h e s o l u t i o n o v e r
e n g i n e , fenders a n d p e r s o n r e m o v i n g
cap. If t h e solution contains f l a m m a b l e
antifreeze, such as alcohol (not r e c o m -
mended f o r use at any t i m e ) , t h e r e is
also t h e possibility of causing a serious
fire.
The pressure-type radiator filler cap contains a
blow off or pressure valve and a vacuum or atmo-
spheric valve (Figure 1). The pressure valve is held
against its seat by a spring of pre-determined strength,
which protects the radiator by relieving pressure if it
exceeds design limits. The vacuum valve is held
against its seat by a light spring, which permits open-
ing of the valve to relieve vacuum created in the sys-
tem when it cools off and which otherwise might
cause the radiator to collapse.
Recovery Bottle
A "see-through" plastic reservoir, similar to the
familiar windshield washer jar, is connected to the
radiator by a hose. As the car is driven, the coolant is
heated and expands. The portion of the fluid displaced
by this expansion flows from the radiator into the
recovery bottle. When the engine is stopped and the
coolant cools and contracts, the displaced coolant is
drawn back into the radiator by vacuum. Thus, the
radiator is kept filled with coolant to the desired level
at all times, resulting in increased cooling efficiency.
Coolant level should be between "ADD" and "FULL"
marks on recovery bottle. These marks are approxi-
mately two quarts apart so that a 50/50 mixture can be
added (one quart of ethylene glycol anti-freeze and
one quart of water).
G20006-6B
Figure 2 Coolant Recovery Bottle (Typical)
VACUUM RELIEF
PRESSURE RELIEF
G60010-6B-E
Figure 1 Pressure-Type Radiator Cap
The radiator cap is designed to discourage inad-
vertent removal. The finger grips have been removed
so the cap is round in shape. It also must be pushed
downward before it can be removed. A rubber
asbestos gasket is added to the diaphragm spring at the
top of the cap. Embossed on the cap is a caution
against its being opened and arrows indicating the
proper closed position.
Every vehicle has a radiator cap. Also, J, N and
P Series vehicles with 2.0L and 2.5L engines have a
thermostat housing cap. For these engines, add cool-
ant through the thermostat housing (with the thermo-
stat and cap removed).
F A N
Electric Fan
Fans range in sizes from 290mm (11.6 in) to
422mm (16.9 in) with 4 to 7 blades to aid air flow
through the radiator/condenser. The fan is driven by
an electric motor which is attached to the radiator
support.
The fan motor is activated by a coolant tempera-
ture switch. If the vehicle is equipped with A/C, a
second switch can activate the circuit, depending
upon A/C compressor head pressure to the condenser.