The Cooling System

From the radiator to water pump your cooling system keeps your car running down the road.

Your car engine produces lots of heat, and keeping that heat in check is the critical job of the cooling system. Starting at the radiator, we will dive into the cooling system and see what you can do to keep it operating efficiently.

The cooling system is designed to remove heat from the engine to keep the engine operating in it's optimal temperature range. The cooling system is comprised of the following parts...

Water Pump: The water pump is either driven by the fan belt or the timing belt on some newer vehicles. The pump moves coolant from the radiator, through the engine, and back into the radiator. The pump has a shaft with a pulley on one end and a pump rotor on the other end. When the pulley is spun by a belt, the rotor moves the coolant.

Radiator: The radiator is a series of thin channels where the coolant flows through and it cooled by air flowing through it. It is important to keep your coolant in good condition to keep the channels open in the radiator. Following your manufacturers recommendation for changing your coolant, to keep your radiator in good shape.

Thermostat: The thermostat controls the flow of coolant through the engine. When your engine is cold, it actually operates with less efficiency. So until the engine warms up to it's ideal temperature, the thermostat keeps coolant from flowing. Your thermostat can fail in either an open or closed condition. When it fails in the open position, your engine may actually run too cold and you will have bad gas mileage. If the thermostat fails in the closed position, your engine will overheat since no coolant will be flowing through the engine.

Hoses: The hoses carry the coolant from the radiator to the waterpump and from the engine to the radiator. Hoses are generally made of rubber and can deteriorate with time. Hose should be flexible and not dry rotted (check for tiny cracks in the hose)

Coolant: Coolant is generally a mix of water and ethylene glycol. Many times called Anti-Freeze, coolant serves many purposes. As it's common name implies, coolant prevents freezing, but it also provides lubrication for the waterpump, increases boiling point of water, and keeps rust and scale from forming in your cooling system. Coolant must be changed on a regular basis, check your owners manual for the recommended schedule. PH level is critical to keeping your coolant from becoming a metal eating liquid. When you check your coolant for freeze point, also check out the PH level and make sure your coolant has not turned acidic.

Common Problems:

Let's look at the common problems cars have with the cooling system.

• Broken hose. Hoses wear out and can leak. Once the coolant has left the system it can no longer cool the engine and it overheats.
• Broken fan belt. The water pump is driven by the engine through a belt. If the belt breaks the water pump can not turn and coolant will not be circulated through the engine. This will also lead to engine overheating.
• Faulty radiator cap. The radiator cap is designed to hold a certain pressure in the coolant system. Most caps hold 8 - 12 PSI. This pressure raises the point in which the coolant will boil and maintains a stable system. If your cap does not hold pressure, then the car could overheat on hot days since the system never becomes pressurized.
• Water pump failure. Most commonly you will hear a screeching noise and will be able to see coolant leaking from the front of the pump or under the car. Early signs are small spots of coolant under the car after being parked overnight and a strong coolant odor while driving.
• Head gasket... have large amounts of white smoke flowing out of your exhaust? Could be a head gasket. The head gasket seals the cylinder head to the engine block and also seals the coolant passages. When this gasket fails coolant can enter the cylinder and it will be turned to vapor as the engine fires. Head gaskets most often fail after the engine has experienced an overheating situation. When super hot, the cylinder head can warp and allow the gasket to fail.

Preventive Maintenance:

• Check all belts and hoses regularly. (at oil change is a good time)
• Look out for coolant leaks underneath the car, they could be signs of trouble to come.
• Change your coolant every 2 - 3 years depending on the manufacturers recommendations. You can check the freeze point of your coolant with an anti-freeze tester available at any auto parts store.
• Inspect your radiator cap for deterioration of the rubber seal. Replace if you think it is worn. $5 - $10 is cheap insurance.
• Have your coolant system flushed every 5 years. It gets all the corrosion which has built up out of the system.

What to discuss with your mechanic:

• Let your mechanic know when your overheating problems occur. Overheating when idling points to a different problem than overheating at highway speeds.
• Ask your mechanic if it's worth changing the timing belt or chain while he is replacing your water pump. Many times the timing belt turns the water pump so it has to be removed anyway to access the water pump.

WARNING: Never open your radiator when the engine is hot. The pressure in the system can cause hot coolant to splash out and burn you.

Where to next?

• Body
• Brakes
• Cooling
• Drivetrain
• Electrical

• Engine
• Exhaust
• Fuel
• HVAC
• Oil & Lubrication

• Suspension
• Wheels & Tires
• Automotive Schools