Global Machinery Company Sierra 1999 - Manual (Page 326)

yellow blue
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Coolant Surge Tank Pressure Cap
(Gasoline Engine)
The coolant surge tank pressure cap must be fully
installed on the coolant surge tank.
NOTICE:
Your coolant surge tank pressure cap is a 15 psi
(105 kPa) pressure
- type cap and must be tightly
installed to prevent coolant loss and possible
engine damage from overheating.
Thermostat
Engine coolant temperature is controlled by a thermostat
in the engine coolant system. The thermostat stops the
flow of coolant through the radiator until the coolant
reaches a preset temperature.
When you replace your thermostat, an ACDelco
R
thermostat is recommended.