Flow Description

See Figure 6-1. To warm the engine up quickly, the ethylene-glycol coolant is re-circulated through the cylinders (13) and combustion chamber (12) in the cylinder heads. The thermostat (4) blocks the passage to the radiator (11) to recirculate the coolant.

As coolant exits the pump (3), it flows through the crankcase and around the cylinder liners (13) removing the heat build-up caused by the motion of the piston rings. From the cylinder liners (13), the coolant flows up through the cylinder head and around the exhaust valves and combustion chamber (12). After the coolant passes around the combustion chamber (12), it then flows back through the closed thermostat (4) into the pump (3) to repeat the cycle. This flow continues until the coolant reaches 85° C (185° F) and the thermostat (4) opens.

Once the coolant exceeds 100° C (212° F), the thermostat (4) remains open and blocks the by-pass between the entrance and exit ports of the case.

An engine coolant temperature (ECT) sensor is mounted to the thermostat (4). If the temperature should exceed 112.7° C (235° F), the engine coolant temperature indicator on the instrument cluster will illuminate.

After the coolant leaves the cylinder heads, it flows through the radiator coolant inlet pipe (5) to the radiator (11).The eth-ylene-glycol is cooled as it flows through the radiator (11) from left to right.

To increase the amount of air flowing through the radiator (11), two cooling fans will turn on when the coolant temperature exceeds 96° C (205° F) and will turn off when the temperature drops below 91° C (195° F).

The coolant exits the top right of the radiator (11) and flows through the radiator outlet coolant pipe (10) to the coolant pump (3) inlet.

The pressure cap (6) and radiator filler neck pressurize the coolant system. When the coolant pressure exceeds the pressure cap (6) lower limit of 96 kPa (14 psi), the lower valve opens and the excess pressure and expanded coolant flow to the overflow bottle (8) through the overflow tube (7). The overflow bottle (8) is vented to the atmosphere through a long tube (9) which loops over the top of the radiator/oil cooler assembly and down below the coolant level. When the pressure drops, the pressure cap (6) vacuum valve opens to draw coolant back into the coolant inlet pipe (5) from the overflow bottle (8).

Coolant Engine All Part Name

13 12

1. Red - hot coolant

2. Blue - cooled coolant

3. Water pump

4. Thermostat

5. Coolant inlet pipe

6. Pressure cap

7. Overflow tube

8. Overflow bottle

9. Overflow bottle vent tube

10. Coolant outlet pipe

11. Radiator

12. Combustion chamber coolant passages

13. Cylinder coolant passages

Figure 6-1. Engine Coolant Flow


Figure 6-2. Pressure Cap

Upper sealing seat Safety stop Cam

Overflow tube Lower sealing seat

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