MK1 ENGINE COOLING SYSTEM

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Section III. TECHNICAL PRINCIPLES OF OPERATION

TM-5-1940-277-10 Boat Bridge Erection Twin Jet Aluminum Hull Model USCSBMK 1(1940-01-105-5728) MODEL USCSBMK 2 (1940-01-218-9165) Manual

MK-1 FRESH WATER ENGINE COOLING SYSTEM

TM 5-1940-277-10

TM 1940-10/1

1-13. MK1 ENGINE COOLING SYSTEM

a. Flow During Engine Warm Up

During this type of operation the system is divided into two principal circuits (1) and (2), which are almost

independent of each other with a third circuit (3) providing de-aeration.

(1) Thermostatically Controlled Cylinder Block Circuit In this circuit, water is circulated by the conventional engine

mounted water pump 'A', which directs water into the block and then to the cylinder head. From there, the water

is taken by duct 'B' to the water jacket around the exhaust manifold. A small pipe 'C' connects to the header tank

to allow air to escape during filling, also providing a small flow when the engine is running so that continuous de-

aeration takes place. From the exhaust manifold jacket, the water flows through pipe 'D' to the full flow bypass

thermostat. If the water temperature is below the thermostat opening temperature, the flow passes through pipes

'E' and 'F' to the engine oil cooler, and then through pipe i' to the pump 'A', thus completing the circuit.

(2) Low Temperature Circuit

A pump 'H'directs water through pipe 'J' to the gearbox oil cooler, and then through pipe 'K to the charge air

cooler. The water then flows through pipes 'L', 'M' and 'N' to the 'remote cooler'. From the 'remote cooler' the

water returns to the pump 'H' via pipe 'P'. A small pipe 'Q' allows air to escape from the circuit when filling, and

provides continuous de-aeration when the engine is running.

(3) Header Tank Circuit The header tank receives a small flow of water through pipes 'Q' and 'C', and returns make-

up water through pipe 'R', close to the inlet to pump 'A'.

b. Flow When Engine Coolant Is Up To Normal Operating Temperature In this condition the flows described in a

(1), 1 (2) and a (3) continue, but an additional flow circuit is set up which connects the two circuits (1) and (2)

together:

(1) Low Temperature Flow Diluting Thermostatically Controlled Cylinder Block Circuit When the engine thermostat

valve opens, water flows through pipe 'S' and then into pipe 'N' leading to the remote cooler. The water lost from

the engine cylinder block circuit is replaced by water from the low temperature circuit, passing through pipe 'T'

and diluting the 'by-pass' water flowing from 'E' and 'F'. By these means the temperature in the cylinder block

circuit is controlled by the thermostat.