Porsche 928 GTS 1994 Owner's Manual page 74

Checking coolant level in expansion tank
A correctly functioning cooling system requires
only minor care. The coolant level should be
checked from time to time, and always before
going on a longer trip.
The expansion tank with filler cap opening is
located in the right rear of the engine compart-
ment (see illustration). Since the expansion tank
is transparent, it is not necessary to unscrew
the filler cap.
When the engine is cold, the coolant level should
reach the manufacturing seam on the expansion
tank. When the engine is warm, the coolant level
will be above the manufacturing seam.
Since the closed colling system loses almost no
coolant, topping up is normally not required. An
obvious loss of coolant indicates leakage. The
fault will be indicated by a fault message in the
information system display. Top up the coolant
and contact your dealer.
WARNING
Do not open the filler cap when the engine is
hot because of the danger of scalding. Allow
the engine to cool down. Protect your hands,
arms and face.
Using a thick rag, open the cap carefully and
only enough to allow excess pressure to
escape before removing the cap.
To avoid damage to the engine, only add cold
antifreeze and cold water to the cooling sys-
tem when the engine is also cold.
A warm engine should only be topped up if the
coolant level has dropped appreciable below the
manufacturing seam. Too much added coolant
will escape through the pressure cap when
coolant warms up.
For more details see "coolant temperature
gauge and coolant temperature warning light".
Fan control
This device permits cooling output to be
adapted to the operational status of the engine.
A control unit processes the information it re-
ceives from the sensors in the engine compart-
ment and passes the appropriate signals to the
fans. If more air is needed, the speed of the two
continuously adjustable electric cooling fans is
increased. If the temperature of the coolant
drops below 75° C, the fans are switched off; in
the event of a fault, they operate at maximum
speed.
The system has both auto and remote supervi-
sion. Should a component fail, the coolant
temperature warning light gives indication of ex-
cessively high coolant temperatures and a fault
message appears in the information-system dis-
play.
When the engine is warm, the fans may continue
to run after the ignition key has been removed.
To avoid any danger of injury, the fans are
switched off when the engine-compartment hood
is opened. However, this protective measure to
prevent the fans starting suddenly while the
hood is open is only fully operative as long as
the key is removed from the ignition.
Winter operation
At the beginning of the winter season, have the
coolant checked for anti-freeze concentration.
The ratio between water and anti-freeze, neces-
sary to prevent freezing, depends on the antici-
pated outside temperatures. The ratios can be
taken from the mixing chart listed under "Filling
Capacities" or from the container of the anti-
freeze manufacturer.
Increasing the anti-freeze in the coolant
further than shown on the container is not
only uneconomical, it is also detrimental to
engine cooling.
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