Cooling System Description; Radiator Cap - Toyota 22R-E Service Manual

COOLING SYSTEM
DESCRIPTION
This engine utilizes a pressurized water faced circulation cooling system which includes a
thermostat mounted on the outlet side.

RADIATOR CAP

The radiator cap is a pressure type cap which seals the radiator, resulting in pressurization of the
radiator as the coolant expands. The pressurization prevents the coolant from boiling even when
the coolant temperature exceeds 100SC (212SF). A relief valve (pressurization valve) and a
vacuum valve (negative pressure valve) are built into the radiator cap. When the pressure
generated inside the cooling system exceeds the limit (coolant temperature: 110– 120SC (230–
248S F) pressure: 58.8–103.0 kPa (0.6–1.05 kgf/cm
by the pressure and lets steam escape through pipe. The vacuum valve opens to allow atmos–
pheric air to enter to alleviate the vacuum which develops in the cooling system after the engine
is stopped and the coolant temperature drops.
RESERVOIR TANK
The reservoir tank is used to catch coolant which overflows the cooling system as a result of
volumetric expansion when the coolant is heated. When the coolant temperature drops, the
coolant in the reservoir tank returns to the radiator, thus keeping the radiator full at ail times and
ENGINE – COOLING SYSTEM
2
, 8.5–14.9 psi) the relief valve is opened
EG1–223