Operation; Inspection - Yamaha XZ550RJ 1982 Service Manual

CATION:
Take special care so that water pump seals #1
and #2 are not scratched when installing them.
Replace any scratched seal.
THERMOSTATIC VALVE
1. Thermostatic valve

Operation

The thermostatic valve is installed in the water
pump cover and automatically opens and closes the
cooling circuit to regulate the coolant flow depend-
ing on the engine temperature. When the engine is
cool, the thermostatic valve main valve is closed,
but the bypass valve is open. Therefore, the coolant
does not flow into the radiator but flows through the
bypass hose. Further, it flows through the bypass
valve into the water pump, by which the coolant is
pumped to the engine cylinder water jackets. (Fig.
1)
When the engine is warm, the thermostatic valve
main valve is open and the bypass valve is closed.
Therefore, the coolant flows to the radiator where it
is cooled. After cooling, the coolant flows through
the outlet pipe and thermostatic valve main valve to
the water pump, by which it is pumped to the engine
cylinder water jackets. (Fig. 2)

Inspection

1. Inspect the valve face for scratches or other
damage. Replace the thermostatic valve if
scratched or damaged.
2. Immerse the thermostatic valve in the water
as shown. While heating the water, check
the thermostatic valve movement at each
temperature as tabulated. If the thermostatic
valve does not move or is out of specifica-
tion, it should be replaced.
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