Effectivity 912/914 Series
Edition 1 / Rev. 0
75-00-00
page 3
May 01/2007
d02625
BRP-Rotax
Maintenance Manual
2) Systems description
2.1) Cooling system
See Fig. 75-1.
The cooling system of the ROTAX 912/914 Series is designed for liquid cooling
of the cylinder heads and ram-air cooling of the cylinders.
The cooling system of the cylinder heads is a closed circuit with an expansion
tank.
The coolant flow is forced by a water pump, driven from the camshaft, from the
radiator to the cylinder heads. From the top of the cylinder heads, the coolant
passes on to the expansion tank (1). Since the standard location of the radiator
(2) is below engine level, the expansion tank located on top of the engine allows
for coolant expansion.
â—† NOTE: When installing the radiator above engine level, see the latest
respective Installation Manual.
The expansion tank is closed by a pressure cap (3) (with pressure relief valve
and return valve). As the temperature of the coolant rises, the pressure relief
valve opens and the coolant will flow via a hose at atmospheric pressure to the
transparent overflow bottle (4). When it cools down, the coolant will be sucked
back into the cooling circuit. The expansion tank (3) must always be full of
coolant, and the coolant level in overflow bottle (4) should be between the two
marks.
â– CAUTION : Too high pressure in the cooling system might cause damage.
The hose between the expansion tank and the overflow tank
must be free of blockages and the venting bore (5) must not be
closed.
On engines of the 914 Series, the coolant hoses (6) for cyl. 1 and 2 are routed
very close to the exhaust system and are therefore additionally protected by a
heat resistant protection hose.
For winter operation, always use a coolant mixture with a sufficiently low freezing
point (pour point). To ensure trouble-free engine start even at low temperatures,
observe the special directives in the Operators Manual.
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