Tech Tips

Cooling Systems

What is a cooling system?

Your cooling system, using a mixture of water and anti-freeze (coolant), keeps your engine at "normal operating temperature" by transferring heat from the engine to the ambient air via the radiator.

Why is my cooling system important?

The greatest cause of breakdowns is overheating. Gasoline engines have improved a lot but, they are still not very efficient at turning chemical energy into mechanical power. Most of the energy in the gasoline (perhaps 70%) is converted into heat. It is the job of the cooling system to remove that heat from the engine metal, and we're talking a lot of heat! In fact, the cooling system on a car driving down the freeway dissipates enough heat to heat two average-sized houses!

How does it work?

As the engine runs, the engine coolant mixture heats up. On older cars normal engine temperature is about 180° Fahrenheit. On newer cars normal engine temperature can be as high as 235° Fahrenheit. (The reason newer vehicle run at hotter temperatures is because it helps reduce vehicle emissions.)

What is a thermostat?

The thermostat is a bi-metal device. Bi-metal devices have two different metals are laminated together. When heated, these two different metals expand at different rates causing movement of the thermostat. When engine coolant is cold the thermostat moves to the cold position, blocking coolant from flowing through the radiator. When the coolant is reaches normal operating temperature the thermostat moves to the open position, allowing coolant flow through the radiator. When the engine is first started cold, the thermostat is in the closed position. This prevents transmitting the engine heat to the ambient air allowing the engine to heat up faster so passengers can use their foot warmers and windshield defrosters soon after the engine is started. Once the engine reaches operating temperature the thermostat opens allowing coolant to flow through the radiator where the heat from the engine is transferred to the outside air. If the engine is over-heated, it is recommended the thermostat be replaced because running the thermostat higher than normal engine temperature can damage it. When damaged thermostats can stick closed, which can cause an engine to overheat.

What does the radiator do?

The radiator transfers heat from the engine to the to the outside air and thus keeps the engine from running hotter than its design normal operating temperature.

What is a water pump?

The water pump pulls water through a hose from the radiator and pumps it back through the engine. There are many hoses on the typical engine that allows the proper circulation of coolant. The water pump is turned by either a serpentine or V-belt. The belt transfers power from the turning engine to the pump.

How my cooling system be serviced?

The cooling system should be completely flushed and refilled about every 24 months. The level, condition, and concentration of the coolant should be checked periodically. Coolant is a 50/50 mixture of anti-freeze and water. It is recommended that the thermostat be replace when the cooling system is serviced.

Do-It-Yourselfers: never remove the radiator cap until the engine has thoroughly cooled! The system is under pressure and coolant will be forced out violently, if the cap is removed. The tightness and condition of drive belts, clamps, and hoses should be checked by your repair shop.

What happens if my car overheats?

If you don't know why you should not overheat your engine, consider yourself fortunate in never needing to know! Simply put: Do not ever let your temperature gauge climb to the "red" or "hot" zone. If it does, and unless you pull over immediately and shut off your engine, you are likely to be in store for a major repair bill! Naturally, it is very important to have an operational temperature gauge. If you engine temperature gauge is inoperative I would recommend you do not put off having it fixed.

Engines have two major sections- the cylinder head or the "top end," and the engine block "bottom end." These two sections of the engine are separated by a heavy paper-like material called a head-gasket. The head-gasket seals the two sections of the engine together keeping the coolant, the engine oil and the combustion gases confined to their separate areas in the engine. When an engine overheats, depending on the length of time the engine is allowed to operate, there is a range of damage that will occur.

The cylinder head will begin to warp, and the head-gasket will become damaged. Hot combustion gases will leak into the cooling system further hindering the ability of the cooling system to work properly. Disruption of the seal between the two sections of the engine will allow coolant to flow on to the pistons and cylinders washing away lubrication. This damages the pistons first because they are made of aluminum, which is a "softer" metal than the block. However, if it runs long enough the cylinder walls will be damaged. The head gasket also keeps the engine oil flowing to the cylinder head to lubricate the moving parts there. As the head warps the engine oil will be pushed into the cooling system which will cause damage to the hoses, water pump seals, and other rubber parts in the system. Eventually, as enough coolant passes down the cylinder walls to the bottom of the engine, it will be picked up by the oil pump and sent to the various bearings that support many moving parts like the crankshaft, and camshaft, balance shafts and intermediate shafts. As the lubrication is washed away from these bearings friction increases ruining the bearings. Eventually the crankshaft and camshaft will be damaged and if continued to run, will be destroyed.