|
|
| Line 7: |
Line 7: |
| | ==Preamble== | | ==Preamble== |
| | | | |
| − | == WHAT CAUSES OVERHEATING? == | + | ==What causes overheating?== |
| − | Overheating can be caused by anything that decreases the cooling system’s ability to absorb, transport and dissipate heat. A low coolant level, loss of coolant (through internal or external leaks), poor heat conductivity inside the engine because of accumulated deposits in the water jackets, a defective thermostat that doesn’t open, poor airflow through the radiator, a slipping fan clutch, an inoperative electric cooling fan, a collapsed lower radiator hose, an eroded or loose water pump impeller, a water pump that is driven too slowly, or even a defective radiator cap. One of nature’s basic laws says that heat always flows from an area of higher temperature to an area of lesser temperature, never the other way around. The only way to cool hot metal, therefore, is to keep it in constant contact with a cooler liquid. The only way to do that is to keep the coolant in constant circulation. As soon as circulation stops, either because of a problem with the water pump, thermostat, or loss of coolant, temperatures begin to rise and the engine starts to overheat.
| + | The cooling system works by absorbing, transporting, and dissipating heat. Therefore, anything that impedes any of those functions can cause overheating. |
| | | | |
| − | The coolant also has to get rid of the heat it soaks up while passing through the block and head(s). So the radiator must be capable of doing its job, which requires the help of an efficient cooling fan at slow speeds. Finally, the thermostat must be doing its job to keep the engine’s average temperature within the normal range. If the thermostat fails to open, it will effectively block the flow of coolant and the engine will overheat.
| + | *Low coolant level or loss of coolant. |
| | + | *Defective thermostat. |
| | + | *Poor airflow, damaged fan clutch, or broken fan. |
| | + | *Collapsed radiator hose, loose or defective water pump impeller. |
| | + | *Defective radiator cap. |
| | | | |
| − | An important thing to remember when dealing with engine cooling systems: The actual temperature of the coolant is not the most important number, but we use it as an indicator of its performance. The cooling system's job is to transport heat from the engine to the atmosphere. It picks up X amount of heat in the engine (raising its temperature) and deposits Y amount of heat into the atmosphere. If X (the amount picked up) equals Y (the amount given up) then the average temperature stays the same. An example of that is when you're driving and the temperature gauge stays at the same place. If the temperature of the coolant is rising, that indicates its getting more heat than it can dissipate. We usually use the term "overheating" to describe an cooling system that is getting more heat than it can effectively dissipate. The result is rising temperatures to the point of boiling coolant. Boiling coolant means that the surfaces of the water jacket now have a significant percentage of their area covered with steam, not coolant. Steam can't absorb heat as well as coolant and this sets up an exponential problem; more heat, more steam, less contact with coolant, which leads to much higher heat and more boiling. But, back to the X = Y demonstration: As long as X and Y are in balance, the actual temperature of the coolant has little to do with how much heat it is effectively transporting. The effectiveness of a cooling system is with how well its components transport and shed heat, not the actual temperature of the water.
| + | Heat flows from higher temperature to lower temperature. A car's engine is generally cooled by keeping it in constant contact with a cooler fluid. As soon as that circulation is impeded, temperatures rise. The radiator must also be working efficiently to transfer engine heat to the atmosphere, and the thermostat must be in perfect working order. |
| | | | |
| − | It has become commonly assumed, therefore, that cooler is better in the quest to prevent overheating. That is not entirely true. Cooler temps give you more of a buffer; that is to say, it will take more time to reach boiling. But, as shown above, a properly operating and adequate cooling system can operate at almost any temperature under its boiling point. However, if a cooling system is getting more heat than it can dissipate, it will eventually overheat regardless of where the thermostat opens. It is for this reason that using a cooler thermostat doesn't effectively help overheating issues. The temperature of the coolant is a function of heat-in minus heat-out. Overheating occurs when the heat-in is greater than the heat-out.
| + | An engine's cooling system transports heat from the engine, into the coolant, and out into the atmosphere. If the amount of heat that it picks up from the engine is roughly equal to the amount of heat that it dispenses to the atmosphere, the engine temperature will stay constant. "Overheating" essentially just means that the coolant is taking on more heat than it can dissipate to the atmosphere. |
| | + | |
| | + | ===When coolant boils=== |
| | + | When coolant takes on too much heat, it boils. This means that the water jacket surfaces will be covered with more steam than coolant. Steam can't absorb heat like coolant can, and this exponentially exacerbates the problem: more heat results in more steam, which leads to less effective coolant, and, in turn, more boiling of coolant. |
| | + | |
| | + | As long as the coolant is taking on roughly the same amount of heat that it can dissipate, it will be effective. |
| | + | |
| | + | It's easy to assume that cooler temperatures are better. However, they really just give you more of a buffer before the boiling point is reached. However, a properly functioning cooling system can really operate just fine at any temperature under its boiling point. If a cooling system is taking on more heat than it can dissipate, it will eventually overheat, regardless of the temperature at which the thermostat opens. |
| | + | |
| | + | This is why using a lower-temperature thermostat often doesn't solve overheating problems. The heat that the coolant takes on must be roughly equal to the heat that it dissipates. |
| | | | |
| | ==Bulletproof cooling system tips== | | ==Bulletproof cooling system tips== |
Your Privacy Choices