Did you know that up to a third of the heat energy produced by an internal combustion engine ends up as waste heat in the cooling system? A gallon of gasoline produces about 19,000 to 20,000 BTUs of heat energy when it is burned, which is enough to boil over 120 gallons of water! So the two or so gallons of coolant that circulate within the typical automotive cooling system have to carry away a lot of heat. The radiator also has to be fairly efficient at getting rid of the heat, too, otherwise the BTUs will start to back up and make the engine overheat. An efficient cooling system, therefore, requires several things: an adequate supply of coolant, an efficient heat exchanger, a fan to pull air through the radiator at low speeds, a water pump to keep the coolant moving, and a thermostat to regulate the operating temperature of the engine for good performance, fuel economy and emissions. The coolant must also have the right mix of water and antifreeze to provide adequate freezing and boiling protection, and the proper amount of corrosion inhibitors to protect against rust, oxidation and electrolysis. To keep the cooling system in good operating condition, it is important to check the level, strength and condition of the coolant on a regular basis – and to replace or recycle the coolant before the protective additives are entirely depleted. According to the U.S. Department of Transportation, cooling system failure is the leading cause of mechanical breakdowns on the highway. And according to numerous aftermarket surveys that have been performed over the years, coolant neglect is one of the leading causes of cooling system breakdowns. The coolant reservoir is usually transparent with FULL and LOW marks on the side (or HOT FULL and COLD FULL). Maintain the coolant level close to the FULL mark. Add coolant if the level is low. Do not overfill. How To Check Your Car's Coolant Level CAUTION: Never open the radiator cap on a hot engine. Hot steam can blow out and possibly burn you! Wait until the engine cools to open the radiator or coolant reservoir cap. One reason for checking the coolant level regularly is to detect leaks that can lead to overheating. The level should be checked at the coolant reservoir, not the radiator, because the radiator will siphon coolant from the reservoir when it is needed. Most vehicles will lose a little coolant over time due to evaporation from the reservoir. But a significant loss of coolant in a relatively short period of time usually signals a leak, a radiator cap that is not holding pressure or a cooling system that is running too hot. Visually inspect the radiator, water pump, hoses, freeze plugs, etc. for external leaks, and then pressure test the radiator and cap to find out where the coolant is going. A tight system should hold the maximum rated pressure for at least two minutes with no drop in the gauge reading. If you do not see any visible leaks and the system holds pressure, make sure the cap is good and has the correct pressure rating for the application (somebody may have replaced it with the wrong cap). Still cannot find where the coolant is going? Check the automatic transmission dipstick. A leaky ATF oil cooler loop in the radiator may be allowing ATF fluid and coolant to intermingle. If the system does not hold pressure, you have found an internal leak. Now you have to figure out where. Check the level and appearance of the oil on the dipstick for coolant contamination in the crankcase. A higher-than-normal oil level and/or a foamy appearance to the oil or droplets of coolant on the dipstick would tell you the engine has a leaky head gasket or cracked block. Coolant leaking into a combustion chamber past the head gasket or through a crack in the cylinder head will often foul the spark plug and contaminate the oxygen sensor. The silicate corrosion inhibitors in conventional antifreeze will poison the O2 sensor, so plan on replacing the sensor(s) if this has happened. If no leaks are found, the loss of coolant may be due to long-term neglect or a temporary episode of overheating. Has your engine overheated recently? A defective cooling fan, slipping drive belt, exhaust restriction (plugged converter) or even overloading the engine may have caused the system to get too hot and boil over. Testing the Strength of the Coolant Checking the strength of the coolant to determine the concentration of antifreeze in the coolant is just as important for hot weather driving as it is for cold weather. A 50/50 mixture of ethylene glycol (EG) antifreeze and water will provide boiling protection up to about 255 degres F with a 15 psi cap, and freezing protection down to -34 degrees F. By comparison, a 50/50 mixture of propylene glycol (PG) antifreeze and water will provide boiling protection to 257 degrees F and freezing protection to -26 degrees F. Increasing the concentration of antifreeze in the coolant will raise its boiling temperature and lower its freezing point. Even so, the maximum concentration of antifreeze should usually be limited to 65% to 70% because too much antifreeze and not enough water reduces the coolant's ability to carry heat – which increases the risk of overheating in hot weather. Something else to keep in mind is that EG and PG antifreezes have slightly different specific gravities (densities), so be sure you use the correct type of hydrometer, refractometer or test strip when checking the coolant. Chemical test strips can reveal both the strength and condition of the coolant. Add antifreeze if the strength is low. Replace the coolant if the corrosion protection is borderline or low. Check The Condition of the Coolant You cannot judge the condition of the coolant by appearances alone. It may look like new, but if the chemistry is not right the coolant can be a potential time bomb just waiting to cause problems. Most antifreeze is about 95% ethylene glycol by weight, with the remainder being corrosion inhibitors and other additives. Time and heat eventually deplete the protective additives, leaving the system vulnerable to internal corrosion. Ethylene glycol never wears out, but the additives do so that is why the coolant needs to be changed or recycled after so many chilometri. Keeping the coolant up to snuff is especially important for vehicles with bimetal engines (iron block and aluminum heads) and those with aluminum radiators because aluminum corrodes more quickly than iron when the coolant chemistry turns sour. Severe corrosion from coolant neglect inside a copper/brass radiator. The old rule of changing the coolant every two years or 30,000 chilometri is still valid for "conventional" green and yellow coolants. But the same also applies to systems filled with long-life coolant that may have been contaminated with conventional coolant. If long-life and conventional antifreeze are intermixed, the interaction between the additive packages can reduce the life of the long-life antifreeze from five years/150,000 chilometri down to that of ordinary antifreeze. Unfortunately, it is difficult to tell if a system filled with long-life antifreeze has been topped off or intermixed with ordinary antifreeze. Dex-Cool in General Motors vehicles is dyed orange to distinguish it from ordinary coolant, but it takes a lot of green or yellow coolant to produce a noticeable change in color. If in doubt, it is always safer to err on the side of caution and go with the shorter service interval. The best way to check the condition of antifreeze is with a chemical test strip that shows how much reserve alkalinity (which prevents corrosion) is left in the coolant. The test strip changes color when dipped in the coolant, allowing you to compare the color against a reference chart to determine the coolants condition. If the coolant tests bad or is close to borderline, replace or recycle it. Rejuvenating The Coolant There are three ways to rejuvenate old coolant: 1. Recycle It. Take your vehicle to a shop that offers a coolant recycling service. Recycling machines can filter, clean and restore your old coolant to like-new condition. One of the main advantages of recycling is that it reduces hazardous waste disposal problems by concentrating harmful pollutants. 2. Treat It. Chemical additives are available that claim to restore corrosion protection without having to change the antifreeze. But, as any coolant chemist will tell you, such additives are a shotgun approach that may or may not achieve the desired results. One additive you can use for preventive maintenance is a cooling system sealer. It should be the type that "melts" and circulates with the hot coolant. Bars Leak is a god choice here. As long as the sealer remains in the system, it will plug any small leaks that might develop (like pinholes in a heater core or seepage in a head gasket). Sealers can also prevent porosity leaks in aluminum heads, intake manifolds and blocks. That is why many engine rebuilders place a few cubes of sealer inside their engines. They know from experience that it reduces the risk of a comeback by preventing coolant leaks throughout the cooling system. 3. Flush & Replace It. Flushing is a must when draining and refilling the cooling system because flushing removes most of the old coolant from the engine block. It also helps dislodge accumulated deposits that can plug heater cores, radiators and interfere with proper heat transfer. Just draining the radiator can leave 30-50% of the old coolant inside the engine. If the coolant contains sediment or there is evidence of scale buildup in the radiator or engine, a chemical cleaner should be used to remove the unwanted deposits. Good Coolant Protects Your Car's Radiator Maintaining the coolant will go a long ways toward prolonging the life of the radiator and other components in the cooling system. But if the coolant is not maintained, corrosion will eventually take over and attack the innards of the system. The most vulnerable components are the radiator and heater c…

Fonte: AA1Car.com