Engine Cooling Systems Explained
The purpose of the engine's cooling system is to remove excess heat from the engine, to keep the engine operating at its most efficient temperature, and to get the engine up to the correct temperature as soon as possible after starting. Ideally, the cooling system keeps the engine running at its most efficient temperature no matter what the operating conditions are.
As fuel is burned in the engine, about one-third of the energy in the fuel is converted into power. Another third goes out the exhaust pipe unused, and the remaining third becomes heat energy.
A cooling system of some kind is necessary in any internal combustion engine. If no cooling system were provided, parts would melt from the heat of the burning fuel, and the pistons would expand so much they could not move in the cylinders and the engine will sieze.
The cooling system of a water-cooled engine consists of: the engine's water jacket, a thermostat, a water pump, a radiator and radiator cap, a cooling fan (electric or belt-driven), hoses, the heater core, and usually an expansion (overflow) tank.
On the other hand, if an engine runs at too low a temperature, it is inefficient, the oil gets viscous (adding wear and subtracting horsepower), deposits form, and fuel mileage is poor-- not to mention exhaust emissions! For these reasons, the cooling system is designed to stay out of the action until the engine is warmed up.
Cooling System Components
DEFINITIONS:
Radiator:
The radiator is the key to the entire cooling system, it is the part that actually transfers the excess heat produced in the engine to the outside air. It is made up of several rows of small tubes connecting two containers which hold the coolant. Small fins are placed around the tubes to direct air around the outside of the tubes and to help the heat transfer from the tubes to the outside air.
Radiator hoses:
The radiator hoses don't do much except transport the coolant into and out of the radiator. The normal flow is from the lower hose to the water pump, through the cooling passages in the engine, and back through the thermostat to the upper hose and then to the radiator.
Water pump:
The water pump furnishes the force that moves the coolant around the system. Most common problem is a leak that will appear at the small hole that you can see near the shaft if you look closely. This leak isn't a problem if you make sure that you top up the system on a regular basis.
Thermostat:
The thermostat blocks off the main path for the hot coolant to return to the radiator, causing a large portion of it to be directed through the heater core and back to the engine until it reaches normal operating temperature and the thermostat opens. At this point coolant starts to flow to the radiator through the upper radiator hose. This function makes your heater produce heat faster, as well as helps the engine warm up quicker.
Heater hoses:
Transport coolant to and from the heater core. Look for leaks at the hose clamps where they connect to the heater core and the engine.
Heater core:
A mini-radiator that is used to heat the air inside the car. The hot coolant
flows through the tubes and air is directed through the fins, absorbing
the heat and then being directed to the cab or to the windshield defrost
vents. When your heater core starts to get plugged up, you will gradually
get less and less heat from your heater.
Coolant:
The vast majority of cars use a 50-50 mix of ethylene glycol and water for coolant, which also gives anti-freeze and anti-corrosion protection. In extreme cold climates, a mixture of up to 75% antifreeze to 25% water is used. Don't try to run your car on pure anti-freeze! The engine will overheat. If you use distilled water for the mix, you'll have significantly less corrosion.
Radiator cap:
The cap just keeps the coolant from sloshing out of the radiator and it maintains a positive pressure in the cooling system. Since the boiling temperature of the coolant is dependent on the pressure, this feature is necessary for proper functioning of the system.
Thermostat:
The thermostat is probably the cheapest part of the cooling system. Mainly for this reason, every customer that comes in the door with an overheating problem is required to say, "It's probably the thermostat." This is a law of nature. The thermostat has one job, that is to block the main coolant return passage to the radiator until the engine heats up to operating temperature. Then the thermostat opens and the coolant circulates. If the top radiator hose gets hot, and coolant flows freely into the top of the radiator, then the thermostat is opening. Still, a new one can't hurt, and most of them are fairly easy to replace, so why not?
Bypass hose:
The bypass hose allows a small portion of the coolant to circulate when the thermostat is closed. Some engines don't have a bypass hose, but rather a bypass passage that is part of the engine cooling jacket. Not much to go wrong, unless the hose develops a leak. regularity.
Flushing My Radiator?
So, you need a coolant flush? Let's talk a little about the coolant first. There are 2 types of coolant used in your cars today. First, you have the green anti-freeze(ethylene-glycol) this used to be the most common type of anti-freeze used and it does a great job. The second type of coolant used is dex-cool (extended life coolant) this coolant is orange in color and is supposed to last 100,00 miles. Both types use a 50/50 mix with water.
Most people think of a coolant flush as a high pressure flushing system through your radiator. There are some good chemicals out there that will remove some of the corrosion in your cooling system, but if the cooling system is in that poor of a condition flushing will probably not help very much. The best thing you can do for your cooling system is change the coolant every 2 years. Just a simple drain and refill will add years to the life of your cooling system.
But what about extended life coolant? Well, I know its supposed to last 100,000 miles but that is absolutely NOT true! Dex-cool is extremely corrosive to your cooling system if not maintained properly. Always replace your radiator cap when you change your coolant. This is also a good time to inspect the hoses. Always check for leaks or bulges with the engine cold, squeeze the radiator hoses with one hand at all points along the hose. If soft spots, bulges, or a "cracking feeling" is identified, replace ALL water hoses at the same time.
