HVAC and Radiators



Aporte hecho por: Alicia Regina Pérez, Carné UVG-98164

It's no secret there are new air conditioning systems in place in today's vehicles. But, do you know why? Do you know what your options are if you're still using and old R-12 air conditioning system?

This section provides not only the reason for a new system in vehicles, but also how air conditioning, radiators and other heating and cooling systems operate.

Your Cooling System

The Parts That Make It Tick. All the parts of the cooling system need to work together to prevent engine trouble. Here's how the various parts of your cooling system work and how Prestone® brand products help keep them running.

The Engine: This is the power station of your car. Gasoline and air are ignited inside its combustion chamber to produce intense heat and mechanical energy. Over time, such high temperatures could damage the metal surrounding the chamber. By helping to remove excess heat, Prestone® antifreeze/coolant keeps the engine running efficiently.

The Radiator: Hot coolant from the engine flows through tubes which conduct coolant heat to a honeycomb of small metal fins which are cooled by air. If you neglect your coolant, radiator metals can rust or corrode. This corrosion can eat holes in the thin, lightweight aluminum radiator parts, especially in newer vehicles. Rust and corrosion can also clog any radiator over time. To prevent this build-up, Prestone recommends regular cleaning with Prestone® Super Flush. Using Prestone® antifreeze helps prevent corrosion build-up and eliminate radiator leaks to begin with.

The Thermostat: This valve controls the amount of coolant flowing from the engine to the radiator. In warm weather, when the engine is hottest, the thermostat opens freely to allow the free passage of coolant. In cool weather, it stays nearly closed, since maximum cooling isn't necessary. Well-maintained thermostats help maintain optimum engine temperature in cold and warm climates.

The Heater Hose And Core: Some engine heat is carried by the antifreeze to the heater core to heat the passenger compartment. The car's antifreeze/coolant is also routed here, via heater hoses, to prevent rust and corrosion. Prestone antifreeze/coolant is designed to help prevent corrosion within the heater core without harming rubber hoses.

Automotive Cooling and Heating System Components

  1. Heater Hose
  2. Heater Control Valve
  3. Thermostat
  4. Radiator Hose
  5. Overflow Reservoir
  6. Heater Core
  7. Engine
  8. Coolant Pump
  9. Fan
  10. Radiator

Auto Fluids and Safety

Auto fluids, including antifreeze, are essential to your car's health. But many can be toxic to people and pets.

Fortunately, when handled, stored and disposed of properly, these products can be used safely.

These instructions and safety tips will help you create a safer environment for using these important fluids - and keep your cooling system running smoothly.

What Is Antifreeze And Why Is It Important?

Antifreeze protects a vehicle's cooling system from temperature extremes, rust and corrosion. It prevents the radiator from boiling over during hot weather or freezing during cold weather. Since cooling system failure is a leading engine-related cause of roadside breakdowns, antifreeze maintenance is an important preventative measure.

The main ingredient in most standard antifreezes is ethylene glycol (EG). Prestone® antifreeze/coolant combines EG with special additives called "inhibitors" to protect engine radiators and water pumps against rust and corrosion.

Cooling Systems

It is the job of the cooling system to remove heat from the engine that is produced during the combustion process (figure 12). The cooling system generally consists of the following components:

A mixture of coolant and water is circulated through the water jacket of the engine, where it absorbs heat from around the cylinder walls, spark plugs, and valves. The hot coolant then flows from the water jacket through the thermostat, that is calibrated to open at a certain temperature, to the radiator. Air, supplied from a fan and the motion of the vehicle, moves through the radiator and carries away the heat. The cooling system is kept under pressure by the radiator pressure cap, which raises the boiling point of the coolant, improving its efficiency.


heater core

coolant recovery system


heater hoses

water pump


Figure 12, Conventional Cooling System. DELCO


Air Intake

The air intake directs air flow from outside the vehicle through the fins of the condenser and radiator (see figure 13). Obstructions or blockages in this path can cause insufficient cooling of both the condenser and the radiator. Blockage can occur in the fins of the condenser and radiator, as well as in between the two components.

Insufficient cooling can also be the result of misdirected airflow. Misdirection of airflow permits air to bypass the condenser and radiator. Misdirected airflow is usually the result of missing or damaged components in the air intake system.

Figure 13, Air Intake. DELCO



The radiator is used to remove heat from the engine (figure 15). It radiates the engine heat through the fins. The air directed through the fins absorbs the heat and removes it from the coolant. If the radiator becomes saturated with heat, resulting from excessive engine temperatures or insufficient airflow, the heat will transfer to the condenser. This heat transfer results in poor operation of the A/C refrigeration system.

The dissipation of heat from the radiator is affected by vehicle speed, coolant fan operation and correct operation of the air intake system.

Most electric coolant fans are ECM/PCM-controlled based on inputs from the coolant temperature sensor, A/C coolant fan pressure switch and vehicle speed sensor. The following are three configurations of electric coolant fans:

Figure 15, Radiator