Cooling System Operation

The cooling system is designed to be a "closed" system. This means that any air leaks will lead to reduced cooling capacity.

Why a "closed" system? Because pressurizing a liquid raises it's boiling point past approx 212 Fahrenheit. If the coolant was not under pressure, it would boil off before it could cool the engine.

There are 8 main components in the cooling system (not including the hoses)

• Waterpump
  • Pushes coolant from the motor into the top of the radiator and the rest of the cooling system
• Radiator
  • Holds the majority of coolant in the system.
  • "Fins" on the front decrease temperature of the coolant inside the radiator
  • Hot coolant in at the top, cooled out the bottom
• Radiator Cap
  • Maintains pressure of the cooling system up to a specific PSI
  • Once PSI has been bypassed it allows pressurized coolant to be released to the atmosphere
• Recovery Bottle (Overflow Tank)
  • As coolant heats up, it expands and the "extra" coolant needs to be "held" until needed again
• Fans
  • Push air through the radiator to decrease the temperature of the coolant inside the radiator
• Fan Thermostat (Fanstat)
  • Basically a switch that "turns on" the fans when the coolant temperature rises to a specific degree
  • Also "turns off" the fans when the coolant temperature drops to a specific degree
  • V4's Fanstat completes the ground circuit to the fan motors
• Thermostat (T-stat)
  • Basically a valve that "opens" when the coolant rises to a specific degree
  • Also "closes" when the coolant drops to a specific degree
  • Has a small diameter hole to allow some coolant to flow when the T-stat is closed
• Temperature Gauge Sender
  • Converts the coolant temperature into an electrical voltage - which is converted to an analog or digital display on the instrument panel

Cooling System in Operation

Warm Up

• Fanstat and T-stat are "off/closed".
• Coolant is not circulating in the system (but the water pump still pumps).

Operating Temperature

• Fanstat is "off" but T-stat is "open".
• Coolant is now circulating through the system. The water pump pushes hot coolant from the motor into the radiator (which drops the coolant temperature). The "cooled" coolant then is pushed past the T-stat into the hot motor.
• As the coolant heats up it expands and the "extra" coolant is pushed into the recovery bottle to be used later.
  • If there is a leak in the cooling system, coolant is now pushed out through the leak.

Hot Temperature

• Fanstat is "on" and T-stat is "open".
• Coolant is circulating through the system. The radiator can't drop the temperature of the coolant fast enough, so the fans assist the radiator.

Overheating

• Fanstat is "on" and T-stat is "open".
• Coolant is circulating through the system. The radiator can't drop the temperature of the coolant fast enough, so the fans assist the radiator.
• As the coolant continues to heat up, it increases the pressure in the cooling system. When the pressure reaches the limit in the radiator cap, it releases the pressure by allowing pressurized coolant to expand into the atmosphere (read: drip down the side of the radiator or scald your legs when riding. This is a good indicator that your cooling system needs work)

Cool Down (bike's ignition is off)

• The Fanstat could be "on" or "off", the T-stat could be "open" or "closed" - but the water pump is not pumping
• As the coolant decreases temperature, it contracts and pulls a vacuum on the system. This "contraction" pulls the "extra" coolant from the recovery bottle back into the radiator for use during the next ride.
  • If there is an air leak from the radiator cap to the recovery bottle, the system will pull air into the radiator - instead of the coolant in the recovery bottle. (after the bike is cool - more coolant in the reserve bottle than when you started your ride is a key indicator)

Here is a link to an automotive cooling system with a graphic - which is similar to motorcycles: Automotive Cooling System