Toyota 3R-B 1969, Repair Manual

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C O O L I N G S Y S T E M - Description 7-1
D E S C R I P T I O N
T h e r m o s t a t W a te r P u m p B y - p a s s H o s e W a te r P ip e
R a d ia to r F a n R a d ia to r H o s e W a te r J a c k e t
F i g . 7-1 Engine Cooling S ystem Y6175
T h e cooling system on the 5 R , 3 R - B and 3 R - C engines is of a p r e s s u re fo r c e d
circulation insuring positive cooling efficiency.
T h e construction of the cooling system and the circulation of the coolant a re
shown in the above illustration.
T h e coolant is pumped out from the lo w e r tank of the r a d ia to r, and is fo rc e d ly
circulated within the w a te r jackets provided in the en gin e. A t this tim e, the
majority of the coolant is directly delivered to the w a te r pipe located within the
cylinder head to cool the surrounding of the combustion chambers w h e r e the
engine heats up to the highest temperature during the engine operation. T h e
balance is delivered to the cylinder block through the by-pa ss h ose , and is c i r ­
culated from the cylinder wall to the cylinder head. T h e coolant which has been
heated is returned into the upper tank of the radiator through the thermostat.
If the coolant temperature is lo w , and the thermostat is closed, the coolant is
pumped out from the thermostat chamber and the cylinder block through the b y ­
pass hose (this is r e v e r s e flow when the thermostat is o p e n ed ) , and is d eliv ered
into the w a ter pipe.