Doosan GV158TIC, Operation & Maintenance Manual

Page: 142 / 162

Maintenance of major parts - 136 -
5.4.3. Replacing thermostat and precautions for handling
●
Precautions for handling
The wax pallet type thermostat does not react as quickly as bellows type one to a variation of tem-
perature of coolant. Such relatively slow reaction is mainly due to the large heat capacity of the wax
pellet type thermostat. Therefore, to avoid a sharp rise of coolant temperature, it is essential to idle
the engine sufficiently before running it. In cold weather, do not run the engine at overload or over-
speed it immediately after starting off.
●
When draining out or replenishing coolant, doing it slowly so that air is bleed sufficiently from the
entire cooling system.
●
Replacing thermostat
If the thermostat is detected defective, replace with a new one.
5.4.4. Diagnostics and troubleshooting
Condition Possible causes Corrections
1. Engine over
heating
●
Lack of coolant
●
Radiator cap pressure valve spring
weakened
●
Fan belt loosened or broken
●
Fan belt fouled with oil
●
Thermostat inoperative
●
Water pump defective
●
Restrictions in water passages due to
deposit of scales sages
●
Ignition timing incorrect
●
Restriction in radiator core
●
Gases leaking into water jacket due to
broken cylinder head gasket
●
Replenish coolant
●
Replace cap
●
Adjust or replace fan belt
●
Replace fan belt
●
Replace thermostat
●
Repair or replace
●
Clean radiator and water passages
●
Adjust ignition timing correctly
●
Clean exterior of radiator
●
Replace cylinder head gasket
2. Engine over
cooling
●
Thermostat inoperative
●
Ambient temperature too low
●
Replace thermostat
●
Install radiator curtain
3. Lack of coolant
●
Radiator leaky
●
Radiator hoses loosely connected or
damaged hoses
●
Radiator cap valve spring weakened
●
Water pump leaky
●
Cylinder head gasket leaky
●
Cylinder head or cylinder block cracked
●
Correct or replace
●
Retighten clamps or replace
●
Replace cap
●
Repair or replace
●
Replace cylinder head gasket
●
Replace cylinder head or block
4. Cooling system
noisy
●
Water pump bearing defective
●
Fan out of balance
●
Fan belt defective
●
Replace bearing
●
Replace fan
●
Replace fan belt