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Cooling Systems Questions • What is an air cooling system, what does it do and its components • Some manufacturers recommend changing engine coolant every two years. Explain why this service is recommended and what is involved in changing the coolant in a liquid cooling system. Questions • Explain what causes the pressure in a liquid cooling system and explain why liquid cooling systems are pressurized. • A liquid cooling system is continually low on coolant. Where can this coolant be going? Example – external leaks – covers all leaks from the cooling system that would eventually end up on the ground. Where else could it be going? In Order To Properly Maintain And Identify Preventable Problems To Cooling Systems Understanding the Operation And Principles Of Cooling Systems is Required. Cooling systems are designed to(3) • Remove excessive heat produced by the engine during combustion and by friction. • Get the engine up to operating temperature as quickly as possible. • Maintain the engine at its’ optimum operating temperature. • Engines only turn about 33% of the heat produced during the combustion process into usable energy. The Rest has to be removed • How is this done?(2) • Cooling systems are only capable of removing about 30% of the heat produced by the combustion process. • The exhaust and heat radiating from hot components looks after the rest. Types of Cooling Systems(2) • Air Cooling • Liquid Cooling Air Cooling Systems – Pros and Cons Air Cooled engines are light and use a very simple cooling system. Have few if any moving parts. Require little or no maintenance. Cannot cool as efficiently as liquid cooling systems. Liquid Cooling Systems Use antifreeze (a 50/50 mix of water and ethylene glycol). This antifreeze circulates through the engine absorbing and carrying away some excess heat with it. These systems are heavy and have many parts which require maintenance. They cool an engine far more efficiently than an air cooling system. Get the engine up to operating temperature faster than air cooling. Air cooling system components Air fins – these air fins are placed around the cylinder and cylinder head. Passing air carries the excessive heat away as it passes through the fins. Engines not moving through the air at a sufficient speed use a fan to blow the air through the fins. Shrouds – (metal or plastic panels) can guide the air past the cooling fins. The only maintenance required is cleaning of the air fins and fan (if equipped), possibly a belt (driving the fan) may need adjustment or replaced. Problems: • It is difficult to control the warm-up time with an air cooled engine. (outside air temperature plays a major roll) • It is difficult to cool the engine evenly. (getting the air to flow evenly around the engine) • Because of this air cooled engines have hot spots. • Very difficult to heat the passenger compartment of the vehicle. • Little or no warning of the engine overheating. Benefits • Light weight (almost no extra weight added to the engine) • Few or no moving parts. (nothing to wear) • Do not rob the engine of power. • Require virtually no maintenance. • Cost is far less than a liquid cooling system. Never • Paint the air fins on an air cooled engine! (even if they are painted from the factory) • Operate an air cooled engine with the fins plugged with anything. (mud, road tar) • Allow an air cooled engine to operate without air flowing through the air fins. (use a household electric fan if necessary) • Drive a hot engine into a deep water hole too quickly. (ATV – could crack the engine) • Run an engine, designed with air shrouds, without them. Always • Keep the air fins clean and free of debris. (grass, leaves, sawdust etc.) these can cause overheating or even a fire. • Keep fans and or belts clean and adjusted properly. • There your maintenance is done. STOP Little Quiz 1. List two types of cooling systems. 2. Cooling systems remove about 33% of the heat produced by the engine. Where does the other 67% go or do? 3. List 5 benefits of air cooling systems. 4. What are a few shortcomings of an air cooled engine? 5. What maintenance or precautions are necessary for air cooling systems? Liquid Cooling Systems • Many components means much maintenance. • Just keeping the coolant in the vehicle can be a problem. • The density of the coolant is important. (especially on turbo charged vehicles) • Anti freeze is poisonous and will pollute wells. Parts Requiring Maintenance • Belts – the water pump is belt driven and the belt needs to be maintained and or adjusted. • Hoses – deteriorate in time and have to be checked and possibly replaced. • Radiator – fins must be checked and possibly cleaned from time to time. • Thermostat – must be replaced according to the maintenance schedule or when defective. • Radiator cap – both valves and seals must operate properly (pressure and vacuum). • Coolant – must be changed because the additives get used up. Anti freeze • Flows through the engine absorbing heat as it travels. • Is used to heat the passenger compartment. • Has additives to protect all the aluminum and metal parts. • Contains a lubricant for the water pump, rad cap and thermostat. • Service life is usually two years. • Is poisonous to: pets, children and even fools. • Is colorful and sweet tasting (to make things worse) Leaks • Cooling system leaks can be difficult to find. • External leaks are the easiest. Coolant leaking on the ground (problem should be obvious). Check hoses, water pump, radiator and engine gaskets. • Internal leaks – leaks inside the engine can cause serious engine damage. Coolant in the oil or getting into the combustion chamber and being burnt by the engine. • Coolant entering the engine oil will cause a white milky looking oil. • Coolant being burned by the engine will turn sparkplugs (country snow white). Possibly cause the engine to miss when first started and run properly after a few seconds of operation. Cause a very sweet smell coming from the exhaust. • Leaks inside the vehicle. These could be a heater core or the plumbing inside the vehicle. The first sign is the windshield steaming up when the heater is on defrost setting. •Leaks into the automatic transmission cooler. This can be either transmission fluid in the cooling system or worse yet coolant into the automatic transmission or both. Radiator Caps Have two seals. One to hold pressure in the cooling system and one to prevent spilling fluid onto the ground (make sure the expanding fluid goes to the overflow bottle. Two Valves • A pressure relief valve is used to prevent the cooling system from becoming over pressured and result in leaks or broken parts. • A vacuum valve is also part of the radiator cap and this valve allows the overflowed coolant back into the engine as the coolant cools. The coolant contracts as it cools and creates a vacuum in the cooling system. Just a good time to ask • What causes the pressure in a cooling system? • Its not the water pump. • Its not the radiator cap. • Its not the thermostat. • It’s the heating of the coolant by the combustion heat. That’s right as we heat a fluid it expands and thereby creating the pressure in the cooling system. • Keeping pressure in the cooling system allows higher engine operating temperatures without boiling the coolant. (engines run more efficiently at higher temperatures) • Up to 110-115 degrees Celsius is acceptable and that is 10-15 degrees above the boiling point of water. • If the pressure is released quickly the coolant will immediately boil and blow off with great pressure. • This is the reason for not opening a hot cooling system. Never Open HOT Cooling systems get hotter when we shut off the engine. • When the engine is shut off the water pump stops circulating the coolant. • The coolant just sits there absorbing more and more heat. • Shut off a hot engine and about 10-15 minutes later just turn the key on (do not start the engine) and observe the temperature gauge. • This is known as a Heat Soak Condition. Thermostat Thermostats Job • Thermostats are designed to stop or allow coolant flow to the radiator. • When the engine is cold it stops the flow to the radiator allowing the engine to warm- up quickly. • As the engine gets up to a predetermined operating temperature the thermostat opens allowing some coolant to flow to the radiator to be cooled. • So we could say, the thermostat controls engine warm-up and gets the engine up to operating temperature as quickly as possible (more efficient) and maintains it at that temperature. • A thermostat that is stuck in the open position will not allow the engine to warm- up quickly (or at all for that matter) • The first indication is a vehicle that will not warm up the passenger compartment and could be a little hard on fuel • Thermostats are moving parts and do require replacement about every couple of years to be safe. • The days of a hotter thermostat in the winter and a cooler one in the summer are gone. (one temperature for all seasons now) • You should never operate an engine without a thermostat installed. The engine will not get up to operating temperature and waste gas. Remember engines wear more quickly when they are not up to operating temperature. Installation Make sure the thermostat is inserted into the recess or you could break the thermostat housing when you tighten it up. What do you think caused this damage? This thermostat housing was attacked by the coolant either not being aluminum compatible or too old and the anti- corrosion additives have been used up and couldn’t protect the housing. • When the engine is cold coolant flows through the engine water jackets, around the cylinders and cylinder head and to the heater. • This helps the engine warm-up quickly because no coolant goes to the radiator. • This means you should be able to hold onto the upper rad hose when the engine is cold and running and it should not get warm. • If it does get warm, the thermostat is partially open and needs to be replaced. • Once the engine gets up to operating temperature the thermostat opens and then coolant flows everywhere it did with the cold engine plus out through the upper rad hose to the radiator, down through the radiator and back to the water pump through the lower rad hose. • Now you can’t hold onto the upper rad hose. It will be too hot. • Coolant flow is important because when you flush the cooling system you want to make the liquid flow in the opposite direction. (Reverse flushing) Fans • All liquid cooled engines require a fan to move the air through the radiator when the vehicle is not moving at a sufficient speed through the air. • Many different designs are used. Electric Fan Electric fans put very little drag on an engine and can turn on and off automatically when needed. Solid Fan Solid fans are driven by a belt connected to the crankshaft and take a lot of engine power to turn at all times (needed or not). This is the least economical of all fans but is a good choice for plows or trucks working in the woods. Flex Fan These fans are also belt driven from the crankshaft and run at all times. The big difference is that the blades straighten out at high speeds (when a fan is not needed) reducing the drag on the engine. Clutch Fan These fans are driven by a clutch which is driven from a belt connected to the crankshaft. When heat (coming through the radiator) heats up the clutch, it locks up and the fan spins as a solid fan would. Cool air on the clutch unlocks the clutch and the fan “free-wheels” reducing the drag on the engine • Clutch fans (for some reason) are popular on trucks and four wheel drive vehicles. • (thought) - This doesn’t make sense if the vehicle is to be used to plow snow or be driven through the woods at slow speed. • Slow speed operation can prevent the hot air passing through the radiator therefore the clutch will not lock up the fan. (not enough air passing through the radiator at slow speeds) • When this happens the engine can be overheating and the fan will not suck the needed air through the radiator to cool things down. • All you 4X4 nuts keep in mind, a fan turns into a propeller when submerged under water. • This can cause the fan to flex into the radiator. (you’re in trouble now) • Electric fans are popular for these applications as they can be turned off under these conditions and don’t have enough power to hurt anything even if they are running.
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