Doosan G25P-5 Service Manual download pdf (Page 62)

G424F(FE) Service Manual Chapter 3. Engine Mechanical System 60

Cooling System

General Description

Cooling System Schematic

1) Cylinder head. 2) Thermostat. 3) Cylinder walls. 4) Water pump.

Water pump (4) is installed on the front of the

cylinder block. The water pump is driven by timing

bolt.The inlet opening of the water pump is

connected to the radiator lower hose. The outlet flow

from the water pump goes through passages inside

the cylinder block.

The coolant from the water pump through the

cylinder block passages has primary coolant flow to

and around the seats for the exhaust valves. This

method gives the coolant with the coolest

temperature flow to the hottest area during engine

operation.

Cylinder walls (3) are cooled by the coolant flow

through the block. After the coolant goes through the

cylinder block it flows through cylinder head (1) to

the thermostat housing, where the bypass type

thermostat (2) is installed. The thermostat controls

the opening to radiator to control the temperature in

the cooling system.

If the coolant is cold (cool), the thermostat will be

closed. The coolant circulates (makes a complete

circuit) from the water pump and through the

cylinder block until the temperature of the coolant is

warm enough to make the thermostat open. When

thermostat (2) is open the coolant will go through

radiator top hose and into the top tank of radiator.

Coolant then goes through the cores of the radiator.

The air from the fan will make the coolant cool as

the coolant flows to the bottom of the radiator and

out hose where the coolant returns to water pump.

The radiator is equipped with a shroud to increase

the efficiency of the fan and cause the air to be

pushed through the radiator and away from the lift

truck.

If the coolant is hot and the cooling system pressure

is too high, some coolant flows to the top of radiator

through the tube to recovery tank. The cooling

system pressure is controlled by cap. When the

cooling system pressure goes above its rated

pressure, a valve opens in pressure cap which

releases the cooling system pressure to the

atmosphere. After the engine is at normal

temperature for operation, a development of vacuum

is present in the cooling system. Pressure cap

permits air in the radiator to remove the vacuum at

the same time coolant from recovery tank is pulled

back into the radiator.

Cam

Carrier

Cylinder

Head

Engine

Block

Oil Pump

Assy

Belt Driven

“Cassette”

Water Pump

Water inlet

(Actual pump inlet

thru rear of pump)

Water Outlet Assy

(attaches to cyl head)

Coolant

Sensor

Note: Cylinder head gasket orifices control water

flow from block to head.

- Large opening (max flow) at rear of engine

- Small “venting” passages between cylinders

Water out

Oil Pan

* Note: Diagram does not reflect actual engine geometry

Blocking

t/stat

(bypass

open cold)

Upper outlet to

ancillary device

Lower outlet

to water

pump inlet

Cam