Chevrolet Trax: Maintenance overview

ANTIFREEZE/COOLANT

The main function of the Engine Cooling System is to carry heat away from the engine and maintain the desired operating temperature. This is accomplished by circulating antifreeze/coolant through the engine, where heat is generated, and carrying it to the radiator to be cooled.

Over the past decade internal combustion engines have become more fuel efficient; however, most of the energy in the gasoline (perhaps 70%) is converted into heat, and the cooling system keeps the engine from overheating by transferring this heat to the air. But the cooling system also has several other functions.

An automobile engine runs best at a fairly high temperature. When the engine is cold, components wear out faster, and the engine is less efficient and releases more pollutants into the atmosphere. The cooling system is designed to allow the engine to heat up as quickly as possible, and then to keep the engine at a constant temperature.

Modern automobiles operate in a wide variety of ambient temperatures, from well below freezing to well over 100 F. The fluid used to cool the engine must have a very low freezing point, a high boiling point, and it must have the ability to transfer a lot of heat.

An adequate amount of an antifreeze/coolant and water mixture is necessary to reduce the possibility of engine overheating and freezing, and to prevent rust and corrosion in the cooling system.

Water is one of the most effective fluids for holding heat, but water freezes at too high a temperature to be used in car engines. The fluid that most cars use is a mixture of water and ethylene glycol, also known as antifreeze.

By adding ethylene glycol to water, the boiling and freezing points are improved significantly.

The temperature of the coolant can sometimes reach 250 to 275 F (121 to 135 C). Even with ethylene glycol added, these temperatures would boil the coolant. The cooling system is pressurized, which further raises the boiling point of the coolant. Most automobiles have around 14 to 15 pounds per square inch (psi), which raises the boiling point approximately 45 F so the coolant can endure the high temperatures produced in the engine.

Fig. 1: Typical Cooling System

Hoses showing obvious signs of wear such as cracks, cuts, stiffness, bulges, excessive softness or abrasions should be replaced.

The National Automotive Radiator Service Association (NARSA) recommends a seven (7)-point preventative cooling system maintenance check at least once every two years. The program is designed to identify any areas that need attention, and consists of:

• a visual inspection of all cooling system components, including belts and hoses
• a radiator cap test to check for the recommended system pressure level
• a thermostat check for proper opening and closing
• a pressure test to identify any external leaks to the cooling system parts; including the radiator, water pump, engine coolant passages, radiator and heater hoses and heater core
• an internal leak test to check for combustion gas leakage into the cooling system
• an engine fan test for proper operation h a system power flush and refill with car manufacturer's recommended concentration of coolant

VISUAL INSPECTION

What you are looking for is the condition of the belts and hoses. The radiator hoses and heater hoses are easily inspected just by opening the hood and looking. You want to be sure that the hoses have no cracking or splitting and that there is no bulging or swelling at the ends. If there is any sign of problems, the hose should be replaced with the correct part number for the year, make and model of the vehicle. Never use a universal hose unless it is an emergency and a proper molded hose is not available.

Heater hoses are usually straight runs and are not molded, so a universal hose is fine to use and often is all that is available. Make sure that you use the proper inside diameter for the hose being replaced. For either the radiator hoses or the heater hoses, make sure that you route the replacement hose in the same way that the original hose was running. Position the hose away from any obstruction that can possibly damage it and always use new hose clamps. After you refill the cooling system with coolant, do a pressure test to make sure that there are no leaks.

RADIATOR CAP TEST

A radiator cap is designed to maintain pressure in the cooling system at a certain maximum pressure. If the cooling system exceeds that pressure, a valve in the cap opens to bleed the excessive pressure into the reserve tank. Once the engine has cooled off, a negative pressure begins to develop in the cooling system. When this happens, a second valve in the cap allows the coolant to be siphoned back into the radiator from the coolant reservoir. If the cap should fail, the engine can easily overheat. A pressure test of the radiator cap is a quick way to tell if the cap is doing its job. It should be able to hold its rated pressure for two minutes.

ENGINE FAN

The radiator cooling fan is an important part of the cooling system operation. While a fan is not really needed while a vehicle is traveling down the highway, it is extremely important when driving slowly or stopped with the engine running. In the past, the fan was attached to the engine and was driven by the fan belt. The speed of the fan was directly proportional to the speed of the engine; a viscous fan drive was developed in order to disengage the fan when it was not needed.

With computer controls, the engine-driven fans gave way to electric fans mounted directly on the radiator. A temperature sensor determined when the engine was beginning to run too hot and turned on the fan to draw air through the radiator to cool the engine. On many cars, there were two fans mounted side by side to make sure that the radiator had a uniform air flow for the width of the unit.

When the car is in motion, the speed of the air entering the grill is usually sufficient to keep the coolant at the proper temperature and the fans shut off. When the vehicle is stopped, there is no air flow and the fan is turned on when the engine reaches a designated temperature.

When the A/C is turned on the fan circuit would power the fans regardless of engine temperature. The air conditioning system always requires a good air flow through the condenser mounted in front of the radiator. If the air flow stopped, the air-conditioned air coming through the dash outlets would immediately start warming up.

Fig. 2: Typical Cooling Fan

COOLING SYSTEM POWER FLUSH AND REFILL

Old coolant can be replaced by draining it out and replacing it with fresh coolant; however, power flushing will remove all the old coolant and pull out any sediment and scale along with it. Power flushing requires special equipment and generally requires the thermostat to be removed, the lower radiator hose disconnected, and the flush machine connected in line. Water and, sometimes, a cleaning agent are pumped through the cooling system in a reverse path from the normal coolant flow. When completed, the hose is reconnected and a new thermostat is installed. The cooling system is refilled with the appropriate amount of antifreeze to bring the coolant to the proper mixture of antifreeze and water. For most vehicles and most climates, the mixture is 50 /50. In colder climates, more antifreeze is used, but must never exceed 75 percent antifreeze. Follow the vehicle manufacturers' procedures and recommendations.

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