Daihatsu Hijet — Cooling System
Coolant capacity, flush procedure, thermostat testing, and water pump notes.
Specifications
Coolant Flush Procedure
- Ensure the engine is completely cold. Remove the radiator cap and locate the drain plug at the bottom of the radiator. Place a drain pan underneath.
- Open the drain plug and allow the coolant to drain fully.
- Close the drain plug and flush with plain distilled water. Run the engine briefly to circulate, then drain again. Repeat if the flushed water is dark or rusty.
- Close the drain plug and refill with approximately 5.5 L of 50:50 premixed ethylene glycol coolant.
- Leave the radiator cap off. Start the engine and let it warm to operating temperature — the level will drop as the thermostat opens and coolant circulates. Top up as needed.
- Once fully warm, reinstall the radiator cap. Check the level again after the engine has cooled completely.
Thermostat
The thermostat controls flow between the engine water jacket and the radiator. A stuck-open unit causes the engine to run cold and never reach operating temperature. A stuck-closed unit causes rapid overheating — the more dangerous failure.
To test a suspect thermostat, submerge it in a pot of water and heat it on a stove while monitoring temperature with a thermometer. It must begin opening between 82 °C and 88 °C and achieve at least 8.0 mm of travel at 95 °C. Less than 8.0 mm — replace it.
Thermostat replacement requires draining a portion of the coolant and removing the upper radiator hose from the housing. Install with a new gasket or O-ring — do not reuse the old gasket. Refill and run the engine to verify normal operating temperature.
Water Pump
The water pump is driven by the timing belt on the EF-series engine. If you are already in there replacing the timing belt, replace the water pump at the same time — the additional cost is trivial compared to tearing the engine down again if the pump fails later.