Truck Engine Coolant System

Study Notes

Cold Circulation

The water pump initiates coolant flow from the radiator through the engine system when the engine is cranked.
Coolant circulates through the cylinder jackets of the cylinder block and the cylinder head water jackets.
An engine temperature sending unit is located at the collection tube to display water temperature on the panel board.
The thermostat valve operates within a temperature range of 690-800°C in the 5-ton Hino GT truck.
If the coolant temperature is below 690-800°C, the thermostat does not operate, and coolant is redirected through a bypass drill back to the water pump.

Hot Circulation

Continuous operation of the bypass drill allows the coolant to heat up within the system.
When coolant temperature exceeds the thermostat valve's operating range, it expands, redirecting flow towards the radiator instead of the bypass drill.
The coolant moves to the upper tank of the radiator and disperses into its tubes.
Hot coolant is cooled by air passing over the radiator fins, benefiting from a large surface area for effective heat exchange before returning to the lower tank.
Cooled coolant travels back to the water pump via the radiator outlet pipe.

Steam Circulation

At extreme temperatures, some coolant may convert to steam when it reaches the radiator and accumulates in the upper tank.
This steam exerts pressure on the radiator; however, the Pressure Relief Valve (PRV) activates at 3 kg/cm² to release excess steam and prevent damage.
After vehicle operation, steam condenses into water in the upper tank, creating a vacuum.
The Vacuum Relief Valve (VRV) activates at a negative pressure of 20 mmHg, allowing outside air to fill the created vacuum.
In certain setups, the reservoir is positioned under the overflow pipe to capture steam released by the PRV, allowing it to condense back into usable water.

Air Circulation

The cooling fan activates alongside the engine, directing airflow towards the engine.
This airflow aids in cooling the engine and simultaneously generates a partial vacuum behind the radiator, which pulls air through the radiator core for enhanced coolant cooling.
Shroud or deflector plates help direct air effectively across the engine body.

Description

This quiz focuses on the cold circulation process of coolant in a truck engine, specifically the steps involved from the water pump to the thermostat valve. Learn about how coolant flows through the engine components and how temperature is regulated. Perfect for automotive enthusiasts and students in mechanical engineering.