question: What’s the problem with over cooling a car engine?
comment: The engine operates most efficiently when it is already moderately hot. Increasing it's ability to vent heat makes that sweet spot farther away (which is bad if you are just driving casually but good if you are constantly pushing the limit).
passages: Since the heater core relies on the coolant's heat to warm the cabin air up, it obviously won't begin working until the engine's coolant warms up enough. This problem can be resolved by equipping the vehicle with an auxiliary heating system, which can either use electricity or burn the vehicle's fuel in order to rapidly bring the engine's coolant to operating temperatures.
  
  Section::::Air cooled engines.
   Most of driveability issues can be traced back to a few issues:
  
  BULLET::::- Bad ECM earth/ground
  
  BULLET::::- Bad o2/lambda sensor earth/ground
  
  BULLET::::- Faulty Engine Coolant Temperature sensor (ECT)
  
  The engine coolant temperature sensor is located in the coolant flange,(under the 
   Research by the Agricultural Engineering Department of the University of Saskatchewan has shown that operating a block heater for longer than four hours prior to starting a vehicle is a waste of energy. It was found that coolant temperature increased by almost degrees in that period, regardless of the initial temperature. Four tests were run at ambient temperatures ranging from ; continued use of the heater for a further one or two, or more, hours achieved a mere 2 or 3 more degrees Celsius as conditions stabilized. Engine oil temperature was found to increase over these periods by just .
   Finally, other concerns may dominate cooling system design. As example, air is a relatively poor coolant, but air cooling systems are simple, and failure rates typically rise as the square of the number of failure points. Also, cooling capacity is reduced only slightly by small air coolant leaks. Where reliability is of utmost importance, as in aircraft, it may be a good trade-off to give up efficiency, longevity (interval between engine rebuilds), and quietness in order to achieve slightly higher reliability; the consequences of a broken airplane engine are so severe, even a slight increase in reliability is worth giving up other good properties to achieve it.
   If air-cooling proves sufficient for much of the running time (such as for an aero-engine in flight, or a motorcycle in motion), then oil cooling is an ideal way to cope with those times when extra cooling is needed (such as an aero-engine taxying before take-off, or a motorcycle in a city traffic jam). But if the engine is a racing engine that is always producing huge amounts of heat, water or liquid cooling may be preferable.
   Cooling is also needed because high temperatures damage engine materials and lubricants and becomes even more important in hot climates. Internal-combustion engines burn fuel hotter than the melting temperature of engine materials, and hot enough to set fire to lubricants. Engine cooling removes energy fast enough to keep temperatures low so the engine can survive.
  
  Some high-efficiency engines run without explicit cooling and with only incidental heat loss, a design called adiabatic. Such engines can achieve high efficiency but compromise power output, duty cycle, engine weight, durability, and emissions.
  
  Section::::Basic principles.
   Cars and trucks using direct air cooling (without an intermediate liquid) were built over a long period from the very beginning and ending with a small and generally unrecognized technical change. Before World War II, water-cooled cars and trucks routinely overheated while climbing mountain roads, creating geysers of boiling cooling water. This was considered normal, and at the time, most noted mountain roads had auto repair shops to minister to overheating engines.
   It must be kept in mind that the ingestion of small amounts of water into the engine following melting in the carburetor may cause an initial period of rough running for as much as one or two minutes before the power increase is noted. Again, the pilot will note this as evidence that icing conditions are present. However, more than one pilot, when confronted with a rough running engine has mistakenly turned the carburetor heat back off, thereby exacerbating the situation. 
   BULLET::::- Water is generally available should coolant need to be added to the system, but oil may not be.
  
  BULLET::::- Unlike water, oil may be flammable.
  
  BULLET::::- The specific heat of water or water/glycol is about twice that of oil, so a given volume of water may absorb more engine heat than can the same volume of oil.
  
  BULLET::::- Therefore, water may be a better coolant if an engine is permanently producing large amounts of heat, making it better for high-performance or racing engines.
  
  Section::::Examples of engines that are oil-cooled or partially oil cooled.
  
  BULLET::::- HKS 700E
  
  BULLET::::- Wankel engine
   BULLET::::- Heat flow: The flow of heat in the engine is heavily dependent on the porting layout. Cooling passages must be routed around ports. Every effort must be made to keep the incoming charge from heating up but at the same time many parts are cooled primarily by that incoming fuel/air mixture. When ports take up too much space on the cylinder wall, the ability of the piston to transfer its heat through the walls to the coolant is hampered. As ports get more radical, some areas of the cylinder get thinner, which can then overheat.
   The change of air cooling to liquid cooling occurred at the start of World War II when the US military needed reliable vehicles. The subject of boiling engines was addressed, researched, and a solution found. Previous radiators and engine blocks were properly designed and survived durability tests, but used water pumps with a leaky graphite-lubricated "rope" seal (gland) on the pump shaft. The seal was inherited from steam engines, where water loss is accepted, since steam engines already expend large volumes of water. Because the pump seal leaked mainly when the pump was running and the engine was hot, the water loss evaporated inconspicuously, leaving at best a small rusty trace when the engine stopped and cooled, thereby not revealing significant water loss. Automobile radiators (or heat exchangers) have an outlet that feeds cooled water to the engine and the engine has an outlet that feeds heated water to the top of the radiator. Water circulation is aided by a rotary pump that has only a slight effect, having to work over such a wide range of speeds that its impeller has only a minimal effect as a pump. While running, the leaking pump seal drained cooling water to a level where the pump could no longer return water to the top of the radiator, so water circulation ceased and water in the engine boiled. However, since water loss led to overheat and further water loss from boil-over, the original water loss was hidden.
   Some cars, such as the second generation Toyota Prius, pump hot coolant from the cooling system into a 3-litre insulated thermos-style reservoir at shutdown, where it stays warm for up to 3 days.
  
  Section::::History.
   BULLET::::2. Carbon build up behind the intake valves. Since fuel is directly injected inside the combustion chamber, it never gets a chance to wash any contaminants behind the valves. This results in excessive carbon build up over time, hindering performance. Some cars (like the Toyota 2GR-FSE engine in the Lexus IS) combine direct injection with traditional multi port fuel injection to ameliorate this problem
   Engines that do not have a water cooling system cannot heat the cabin via a heater core; one alternative is to guide air around the (very hot) engine exhaust manifold and then into the vehicle's interior. Temperature control is achieved by mixing with unheated outside air. Air-cooled Volkswagen engines use this method. Depending on the design, this can cause a safety issue where a leak in the exhaust system will begin to fill the passenger cabin with deadly fumes.
  
  Section::::Reuse for other purposes.
   However, properties of the coolant (water, oil, or air) also affect cooling. As example, comparing water and oil as coolants, one gram of oil can absorb about 55% of the heat for the same rise in temperature (called the specific heat capacity). Oil has about 90% the density of water, so a given volume of oil can absorb only about 50% of the energy of the same volume of water. The thermal conductivity of water is about four times that of oil, which can aid heat transfer. The viscosity of oil can be ten times greater than water, increasing the energy required to pump oil for cooling, and reducing the net power output of the engine.
   Engines with higher efficiency have more energy leave as mechanical motion and less as waste heat. Some waste heat is essential: it guides heat through the engine, much as a water wheel works only if there is some exit velocity (energy) in the waste water to carry it away and make room for more water. Thus, all heat engines need cooling to operate.
   Thus the application of carb heat is manifested as a reduction in engine power, up to 15 percent. If ice has built up, there will then be a gradual increase in power as the air passage is freed up by the melting ice. The amount of power regained is an indication of the severity of ice buildup.
   The engine produces high temperatures under full application and thus causes a high temperature variation in the engine bay from no operation to normal and full operation. CFRP becomes mechanically stressed over time from high heat transfer effects and thus the engine bay was not constructed from CFRP.
  
  Section::::Design and implementation.:Aerodynamics.
   The Czech Republic–based company Tatra is known for their large displacement air-cooled V8 car engines; Tatra engineer Julius Mackerle published a book on it. Air-cooled engines are better adapted to extremely cold and hot environmental weather temperatures: you can see air-cooled engines starting and running in freezing conditions that seized water-cooled engines and continue working when water-cooled ones start producing steam jets. Air-cooled engines have may be an advantage from a thermodynamic point of view due to higher operating temperature. The worst problem met in air-cooled aircraft engines was the so-called "Shock cooling", when the airplane entered in a dive after climbing or level flight with throttle open, with the engine under no load while the airplane dives generating less heat, and the flow of air that cools the engine is increased, a catastrophic engine failure may result as different parts of engine have different temperatures, and thus different thermal expansions. In such conditions, the engine may seize, and any sudden change or imbalance in the relation between heat produced by the engine and heat dissipated by cooling may result in an increased wear of engine, as a consequence also of thermal expansion differences between parts of engine, liquid-cooled engines having more stable and uniform working temperatures.
   Damage from shock cooling is most commonly believed to manifest itself as stuck valves, cracked pistons and cracked cylinders.
  
  Section::::Analysis.
   Section::::Automotive use.
  
  Waterless coolant is most prominently used in the cooling systems for motorsports, classic car, ATVs, UTVs, snowmobiles and older cars. Older cars often have nonpressurized cooling systems, and the coolant can boil and overflow. Traditionally, this issue has been solved by topping off the radiator with water. This dilutes the coolant and the water can contain minerals harmful to the vehicle. Classic car owners have adopted waterless coolant to solve this problem. Jay Leno uses waterless coolant for his replica 1937 Bugatti Type 57SC Atlantic vehicle.
  
  Section::::Other uses.
   One disadvantage of supercharging is that compressing the air increases its temperature. When a supercharger is used on an internal combustion engine, the temperature of the fuel/air charge becomes a major limiting factor in engine performance. Extreme temperatures will cause detonation of the fuel-air mixture (spark ignition engines) and damage to the engine. In cars, this can cause a problem when it is a hot day outside, or when an excessive level of boost is reached.
  
  It is possible to estimate the temperature rise across a supercharger by modeling it as an isentropic process.
   Section::::Writing and recording.
   Section::::Detection and prevention.
  
  A single cylinder head temperature (CHT) sensor, or in more sophisticated installations, an array of sensors, one for each cylinder, may be employed to monitor the temperature and cooling rate of the engine. Usually a simple analog gauge or a more advanced graphical bar-graph display(see external links below for an image) is used to present information to pilots. Spoilers on the wings or thrust reversal may also be deployed to lose lift without having to reduce engine power substantially, slowing the rate of engine cooling.
  
  Section::::External links.
  
  BULLET::::- "Shock Cooling: Myth or Reality?" at AvWeb.com
   The coolant used in many liquid-cooled engines must be renewed periodically, and can freeze at ordinary temperatures thus causing permanent engine damage when it expands. Air-cooled engines do not require coolant service, and do not suffer damage from freezing, two commonly cited advantages for air-cooled engines. However, coolant based on propylene glycol is liquid to −55 °C, colder than is encountered by many engines; shrinks slightly when it crystallizes, thus avoiding damage; and has a service life over 10,000 hours, essentially the lifetime of many engines.
  