Cooling System Pt. 1

This chapter focuses on the design, construction, and operation of various cooling systems.
Specific systems covered include those for supercharger intercoolers, high-voltage (HV) batteries, HV engine control modules, and hybrid motor-generators.
A thorough understanding of cooling systems is crucial for effective servicing and repair.

Modern vehicles utilize multiple cooling systems to manage the operating temperatures of mechanical and electrical components.
Many vehicle components generate significant heat during operation, such as:
- Internal combustion engine
- Supercharger or turbocharger
- HV battery
- Hybrid drive motor-generator
Without proper cooling, an engine can suffer severe damage within minutes.
Overheating can lead to internal engine parts melting and the engine seizing.

Critical components that require cooling to prevent damage:
- Engine
- Supercharger
- Turbocharger
- Battery pack
- High-power control circuits
Cooling systems facilitate quick warm-up during startup to reduce emissions and wear.
After warm-up, the cooling system maintains a constant operating temperature to prevent overheating.

Keeps the blower intercooler temperature below the engine's operating temperature.
Air compression increases air temperature; cooling prevents detonation and explosions.
Coolant is circulated through an intercooler mounted under the supercharger.

Prevents overheating of the turbocharger under prolonged high boost conditions.
Coolant is circulated through the turbo bearing housing to protect seals, bearings, and the turbine wheel.
High exhaust gas temperatures passing through the turbine housing can cause it to glow red hot.

Uses air or liquid to dissipate heat from battery cells, especially during high amperage draw.
Most vehicles use an electric motor blower fan to force outside air through the battery pack housing.
Warm air is exhausted through ducts.
High-power hybrids utilize liquid coolant circulated between battery pack modules.
Air cooling may be insufficient for high-watt-hour HV batteries.

Employs liquid coolant to prevent motor-generator overheating in electric and hybrid vehicles.
Coolant lines run through the stator housing of large, high-power AC motor-generator assemblies.
Plug-in hybrids can operate in full electric mode for extended distances (e.g., 50 miles/80 km), generating high temperatures.
Circulated coolant transfers heat to a heat exchanger or the engine cooling system.

Forces air or liquid over an aluminum heat sink surrounding high-power transistors.
Power transistors handle high voltages (over 240 volts each, totaling over 600 volts AC three-phase) and high currents (hundreds of amps).
Overheating can cause thermal runaway in transistors, burn out capacitors and resistors, and damage printed circuit boards.
The HV engine control module manages substantial electrical energy and resulting heat.

Most combustion heat is converted into expansion and pressure for piston movement.
Some heat is transferred to engine components.
Without adequate cooling, the engine can be severely damaged in minutes.
Aluminum melts at 1220°F (660°C).
Combustion flame temperatures can reach 4500°F (2500°C).
Iron melts at approximately 2750°F (1510°C).
Steel melts at around 2500°F (1370°C).
The intense heat from the combustion flame necessitates effective heat removal to prevent damage to metal engine parts.

Engine operating temperature is the temperature of the coolant (water and antifreeze mixture) during normal operation.
Typically ranges between 180°F (82°C) and 210°F (99°C).
Maintaining this temperature ensures:
- Correct part clearances due to thermal expansion.
- Proper combustion.
- Optimal emission output levels.
- Peak engine performance.

Rapid warm-up is essential to prevent:
- Poor combustion
- Part wear
- Oil contamination
- Reduced fuel economy
- Increased emissions
Issues with a cold engine:
- Excessive clearance between pistons and cylinder walls due to unexpanded aluminum pistons.
- Thick oil, leading to reduced lubrication and increased wear.
- Inefficient vaporization and combustion of the air-fuel mixture.

Two primary types of automotive cooling systems:
- Air cooling systems
- Liquid cooling systems

Circulate coolant (water and antifreeze solution) through water jackets in the cylinder block and head.
Coolant absorbs heat from metal parts and carries it away from the engine.

Hot coolant flows from the cylinder head to the radiator, then back into the engine block after cooling.
This is the most common coolant flow direction.

Cool coolant enters the head, and hot coolant exits the block to return to the radiator.
Maintains a more uniform temperature, especially around exhaust valves.
Common in high-performance engines.

Utilize an expansion tank (reservoir) and a radiator cap with pressure and vacuum valves.
The overflow tube is routed to the bottom of the reservoir tank.
Pressure and vacuum valve action maintains proper coolant levels.
When the engine heats up, expanding coolant flows into the reservoir.
When the engine cools, coolant is drawn back into the radiator.
This system compensates for small leaks and reduces maintenance.

Basic components:
- Water pump: Forces coolant through the engine and system.
- Radiator hoses: Connect the engine to the radiator.
- Radiator: Transfers heat from the coolant to the air.
- Fan: Draws air through the radiator.
- Thermostat: Controls coolant flow and engine temperature.
The water pump circulates coolant through engine water jackets.
When the engine is cold, the thermostat remains closed, circulating coolant within the engine for rapid warm-up.
Once the engine reaches operating temperature, the thermostat opens, allowing coolant to flow through the radiator for heat dissipation.