Radiator Tips

Function and Design

The radiator is part of the heat exchange family. Other members include: evaporators, condensers, heater cores, and transmission oil coolers.

The function of the radiator is to lower the temperature of the coolant coming from the engine. Coolant temperature is reduced as outside air passes through the radiator. The cooler ambient air extracts heat collected by the coolant and transferred to the radiator.

A radiator is constructed by connecting a core (consisting of small flat tubes) between two tanks. Corrugated, louvered fins are soldered to the tubes to increase the area of hot metal exposed to the radiator core and are assisted by the fan.

Radiators in today's vehicles have been complicated in many ways. Two major complications that affect the radiator's cooling ability are:

1. Automatic transmission oil coolers mounted in the outlet (cold) tank
   of the radiator.
2. Installation of A/C condensers in front of the radiator.

Automatic transmissions produce a tremendous amount of heat that must be removed in order to prevent transmission damage. Hot oil is pumped to the transmission cooler, in effect, a small radiator installed in the radiator's outlet tank. The hot transmission fluid that is added to the tank will raise the coolant's temperature in the outlet tank of the radiator. The cooling system design must allow for the additional heat that is put back into the coolant.

Five Basic Factors That Affect The Operation Of The Radiator

1. Radiator type (downflow or crossflow).
2. Surface area exposed to ram air fins per inch, number of rows
   and fin louvers.
3. Coolant flow (gallons per minute).
4. Volume of ram air.
5. Temperature difference between coolant and ram air.

Factors That Impede Cooling Efficiency

1. Restricted coolant flow through the radiator.
   a. Debris collected at tube openings, due to neglect and "a dirty
   cooling system".
   b. Solder bloom over tube openings, caused by chemical reaction
   between the high lead solder and glycol.
2. Restricted air flow through condenser/radiator. Debris (insects, bugs,
   etc.) can be removed from finned areas with air pressure directed
   towards the vehicle's bumper. Bug screens are not recommended if
   they are not kept clean.
3. Deteriorated radiator cooling fins. This condition is common in
   humid, salty coastal areas. They may also be found where road
   salting is performed for snow removal.

Any of these conditions can cause a vehicle to overheat. Any one or a combination of these factors is an indication of radiator failure. When selecting a replacement radiator, always select a unit that meets or exceeds OE specifications for performance as well as fit.

Radiator Components

Inlet And Outlet Tanks

These tanks house connections for the radiator hose and heater tube. Coolant enters the radiator from the engine through the inlet tank while it exits the radiator and returns to the engine from the outlet tank. These tanks may also have a sensor flange, internal transmission, or engine oil cooler attached.

Core

The core is the body of the radiator and is constructed of tubes and fins made from either brass or aluminum. Heat dissipation takes place in the core.
Tubes - Hot coolant travels through these long narrow tubes to the fins.
Fins - The fins are extremely thin strips of zigzag-shaped copper or aluminum placed between the tubes. As the coolant passes through the tubes, the heat dissipates from the fins.

Advantages Of A High Efficiency Core

• More fins per inch
• More tubes over the height of the core
• More cooling capacity

How To Measure A Radiator

There are two basic radiator designs. They are named for the direction of the coolant flow and can be distinguished by the position of the tanks.

• The first is called a DOWNFLOW. In this design, the coolant flows
  from the top tank to the bottom tank.
• The second type is called a CROSSFLOW. In the crossflow design,
  the coolant flows horizontally from tank to tank.

Before you measure a radiator, make sure it is in the upright position. You will be measuring the core only. The core is the central part of the radiator (between the tanks and the sidepieces) and consists of parallel rows of tubes and fins. MEASURE ONLY THE CORE to determine the size of the radiator.

Core Height

Core height is determined by measuring the distance between the headers of the core. In both diagrams to the left, core height is illustrated by measurement (A). In this catalog, core height is always the first dimension in the illustration section.

Core Width

Core width is determined by measuring the distance between the core side rails. Only the core is measured to determine the width the radiator, not the side rails. In both diagrams to the left, core width is illustrated by measurement (B). In this catalog, core width is always the second dimension in the illustration section.

Core Depth

Carefully insert a piece of wire through the core until the end is flush with the other side. Mark the other end of the wire (at the point where it is flush with the core, withdraw the wire and measure to get the depth. In this catalog, core depth is always the last dimension the illustration section.

Coolant

The cooling system is one of the most important elements in vehicle operation. Key vehicle functions are controlled by data received by monitoring the cooling system. Unfortunately, it continues to remain the most neglected.

The air conditioning condenser is usually installed in front of the radiator. Heat transmitted by the condenser preheats the cooling air before it has a chance to cool the radiator. Cooling systems must allow for the increased temperature of the ambient air and the restricted air flow. These additional heat loads are another reason why more efficient radiators and year-round use of ethylene glycol and water in 50/50 mixture must be used. Automotive coolant is the most obvious and important aspect of properly maintaining the cooling system. Not only is coolant used to keep the engine at a proper operating temperature, it also keeps various metals in the system from corroding.

Manufacturers each have specific recommendations for proper maintenance of this system. On average, they call for the complete replacement of the coolant every two years or 24,000 miles (This is a general guideline. Refer to your vehicles owner's manual for specific details). The coolant can become destructive if the recommended change interval is left unchecked. The coolant's inhibitors and silicates can break down over time and cease to effectively stop corrosion. The fact is, the base chemicals can last longer than this time period without an adverse affect on the coolant's ability to cool the engine. Just remember that although a coolant may look good, it may not be. Follow the manufacturer's recommendations and replace with fresh coolant.