Coolant Heater Description

This vehicle has a pressure-type engine cooling system. A thermostat controls the coolant circulation. The cooling system consists of the following components:
- A radiator
- A radiator pressure cap (gasoline engines)
- A coolant recovery reservoir (gasoline engines)
- A coolant surge tank and surge tank cap (diesel engines)
- A cooling fan and fan clutch
- A coolant pump and pulley
- All related hoses

A 103 kPa (15 psi) radiator or surge tank cap seals the cooling system, causing the system to operate at a higher than atmospheric pressure. The high pressure operation raises the boiling point of the coolant to about 125° C (257° F), increasing the cooling efficiency of the radiator.

The pressure-vacuum valve radiator cap, used with gasoline engines, allows the coolant to expand through the pressure valve in the center of the cap without building up unnecessary pressure. The expanding coolant flows into the coolant recovery reservoir and the vent valve closes because of coolant expansion and flow. Any air in the system is forced into the coolant recovery reservoir and then out of the vent tube at the top of the reservoir. As the system cools, vacuum forces the coolant in the reservoir back to the radiator through the vent valve. Because of this, the radiator remains full at all times.

The diesel engine uses a cooling system with a surge tank. The pressure cap for the diesel engine differs from the gasoline engine pressure cap. The cap is on the surge tank. The diesel engine uses a pressurized surge tank. Coolant circulates through the surge tank. The surge tank allows the escape of any air in the system and provides room for coolant expansion when the coolant is hot.

The cooling system reaches 103 kPa (15 psi) in either system only after the system reaches normal operating temperature.