9. Coolant system
271
9.4 Heat exchanger
9.4.1 Heat exchanger construction
The heat exchanger cools the hot fresh water, that
has cooled the inside of the engine, with seawater.
The cooler core consists of many small diameter
tubes, baffle plates and tube cover.
The seawater flows through the maze formed by
the baffle plates.
There is a reservoir below the cooler core, which
serves as the fresh water tank. There is an
exhaust gas passageway in the reservoir, which
forms a water cooled exhaust manifold.
The pressure cap (filler cap) on top of the heat
exchanger has a pressure valve, which lets off
steam through the overflow pipe when pressure in
the fresh water system exceeds the specified
value. It also takes in air from the overflow pipe
when pressure in the fresh water system drops
below the normal value.
9.4.2 Specifications of heat exchanger
9.4.3 Disassembly and reassembly of
the heat exchanger
(1) Remove the heat exchanger from the
cylinder head. The noise absorber A and
B are installed between the heat
exchanger and cylinder head for 4JH4E/
4JH4-TE/4JH4-HTE engines. Replace if
the absorber deteriorates.
Note:
1) Be careful not to get hurt with the cover A
or B.
2) Be careful not to pour lube oil on the
noise absorbers.
Model Unit 3JH4E 4JH4E 4JH4E-TE/4JH4E-HTE
Tube diameter mm Ø6/Ø5 x 54 Ø6/Ø5 x 54 Ø6/Ø5 x 121
Tube surface area
m
2
0.193 0.347 0.853
Fresh water flow L/hr 3300 3300 3250
Seawater flow L/hr 3080 3080 3300
Fresh water velocity m/s 0.99 0.91 0.82
Seawater velocity m/s 1.61 1.61 1.08
Filler neck
Cooler core
Gasket
Side cover
Side cover
O-ring
O-ring
Pressure cap
Overflow
pipe
010654-00E
3JH4E
Noise
absorber A
Noise absorber B
Cover A
Cover B
Heat exchanger
010655-00E
4JH4E
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