Cooling%20Systems

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Cooling Systems
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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.

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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?

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In Order To Properly Maintain And Identify
Preventable Problems To Cooling Systems
Understanding the Operation And Principles Of
Cooling Systems is Required.
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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.

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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.

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Types of Cooling Systems(2)

• Air Cooling
• Liquid Cooling ?

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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.
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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.
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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.
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• 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.

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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.

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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.

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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.

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• STOP

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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?

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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.

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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.

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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)

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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.

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• 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.

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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.
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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.

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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.
• Its the heating of the coolant by the combustion
  heat. Thats right as we heat a fluid it expands
  and thereby creating the pressure in the cooling
  system.

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• 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.

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Never Open HOT
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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.

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Thermostat
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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.

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• 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

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• 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.

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Installation
Make sure the thermostat is inserted into the
recess or you could break the thermostat housing
when you tighten it up.
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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 couldnt protect the housing.
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• 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.

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• 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 cant 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)

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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.

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Electric Fan
Electric fans put very little drag on an engine
and can turn on and off automatically when needed.
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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.
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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.
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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
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• Clutch fans (for some reason) are popular on
  trucks and four wheel drive vehicles.
• (thought) - This doesnt 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.

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• 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.
  (youre in trouble now)
• Electric fans are popular for these applications
  as they can be turned off under these conditions
  and dont have enough power to hurt anything even
  if they are running.

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