z Replacing thermostat and precautions for handling (1) Precautions for handling The wax pallet type thermostat does not react as quickly as bellows type one to a variation of temperature 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 engine starting (2) When draining out or replenishing coolant, do it slowly so that air is bled sufficiently from the entire cooling system.
(3) Replacing thermostat If the thermostat is detected defective, retrace with a new one. 5.2.3. Diagnostics and troubleshooting Maintenance of Major Components - 128 - Complaints Possible causes Corrections 1.
Engine overheating z Lack of coolant z Radiator cap pressure valve spring weakened z Fan belt loosened or broken z Fan belt fouled with oil z Thermostat inoperative z Water pump defective z Restrictions in water passages due to deposit of scales z Injection timing incorrect z Restriction in radiator core z Gases leaking into water jacket due to broken cylinder head gasket z Replenish coolant z Replace cap z Adjust or replace fan belt z Replace fan belt z Replace thermostat z Repair or replace z Clean radiator and water passages z Adjust injection timing correctly z Clean exterior of radiator z Replace cylinder head gasket 2.
Engine overcooling z Thermostat inoperative z Ambient temperature too low z Replace thermostat z Install radiator curtain 3. Lack of coolant z Radiator leaky z Radiator hoses loosely connected or damaged z Radiator cap valve spring weakened z Water pump leaky z Heater hoses loosely connected or broken z Cylinder head gasket leaky z Cylinder head or cylinder block cracked z Correct or replace z Retighten clamps or replace hoses z Replace cap z Repair or replace z Tighten or replace hoses z Replace cylinder head gasket z Replace cylinder head block 4.
Cooling system noisy z Water pump bearing defective z Fan loosely fitted or bent z Fan out of balance z Fan belt defective z Replace bearing z Retighten or replace fan z Replace fan z Replace fan belt