Cooling system operation

COOLING SYSTEM OPERATION

A = HOT B = COLD

1. Thermostat
2. Radiator top hose
3. Heater matrix
4. Radiator bottom hose
5. Radiator
6. Header tank

The cooling system employed is the by-pass type, allowing coolant to circulate around the engine while the thermostat is closed. This prevents temperature build up in the cylinder head prior to the thermostat opening.

The siting of the thermostat in the inlet, rather than the outlet side of the system, provides a more stable control of coolant temperature in the engine.

When cold, the thermostat closes off the coolant feed from the radiator outlet. Coolant is able to circulate through the bypass and heater circuits, returning back to the engine via the thermostat bulb.

7. Heater valve
8. Water pump
9. Bleed screw
10. Bleed nipple
11. Bleed screw
12. Jiggle valve

As temperature increases the thermostat gradually opens, bleeding cool fluid into the cylinder block and allowing hot coolant to flow to the radiator, balancing the flow of hot and cold fluid to maintain temperature. As the thermostat opens further, so the full flow of coolant passes through the radiator.

Any excess coolant created by heat expansion is returned to the expansion tank via the bleed line. A jiggle valve fitted at the start of the bleed line, prevents pressure build-up in the expansion tank by regulating the amount of returning coolant.

The coolant circulating pump is a rotor type drawing coolant directly from the thermostat, the pump is driven by a geared pulley from the camshaft timing belt.