Keep cool! All about your cooling system.....
Posted: October 3rd, 2012, 10:18 am
Yo fellas,
While doing some research on an overheating problem, I came across this Wiki with loads of useful information on how your cooling system.
http://www.crankshaftcoalition.com/wiki/Bulletproof_cooling_system
It's very informative on how your cooling system works, the different components to it and how they are all related. Easy to read, easy to comprehend and apply to almost any cooling problem you may have.
*note - it's not written specifically for Diesel vehicles, but it applies to almost any vehicle. Also, all units quoted are in Farenheit.
Some snippets from the site:
How the cooling system works
Note- All temperatures are in degrees Fahrenheit.
The cooling system works by absorbing, transporting, and dissipating heat. Therefore, anything that impedes any of those functions can cause overheating:
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.
The 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.
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.
Overheating and its causes
"Overheating" essentially just means that the cooling system is taking on more heat than it can dissipate. 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.
Overheating can be caused by anything that decreases the cooling system’s ability to absorb, transport and dissipate heat. Some causes of overheating are:
Low coolant level, loss of coolant, or insufficient coolant capacity
Buildup of deposits that cause poor conduction of heat into the cooling system
A thermostat that won't open
Poor airflow through the radiator
Damaged or worn fan clutch, or broken fan
Collapsed radiator hose
Loose or defective water pump impeller
Defective radiator cap
Late ignition timing
Bulletproof cooling system tips
Clogging and leaks are two of the most common radiator problems. Bugs, dirt, and debris can block airflow, and limit the radiator's heat-dissipating characteristics. Thus, it's recommended to "back flush" the radiator and cooling system when changing coolant. This helps to clean out deposits, and flushes the remaining coolant from the engine block. You can back flush the radiator by running water through it in the opposite direction of regular flow. Typically, after draining the radiator a t-fitting can be installed in the heater inlet hose. This fitting gets connected to a pressurized water hose, and the system is reverse flushed. Do this until clean water emerges.
A rough guide is to use a radiator at least as large as the one that was originally used to cool the engine, with the same or more radiator cores. However, it's important to note that additional rows don't add a proportional amount of cooling, i.e. a 3-row radiator does not necessarily offer 50% more cooling than a 2-row radiator. This is because subsequent rows receive warm air from the rows in front of them. However, adding radiator frontal area IS proportional, but this usually causes fitment issues, so additional rows are generally the only viable choice. Also the radiator design and materials can have an effect on the radiator efficiency; a larger radiator is not necessarily a better radiator.
Oftentimes, the cheapest and most bulletproof way is to use the largest radiator that will fit, along with the fan type and size, and shroud that was designed for the radiator from the factory.
Use a full shroud, with the radiator positioned so that the fan blades are half-in and half-out of the shroud hole, and no more than 1" of clearance between the shroud and the fan blade tips (just enough to prevent interference when the motor rocks on its rubber mounts).
Fan recommendations: OEM 18 inch, 7-blade steel fan with 2" to 2-3/4" pitch. The pitch of a fan can be measured by laying the fan down on a flat surface and measuring from the flat surface to the edge of the fan blade. Fans that are relatively flat (such as a flex fan) may not move enough air at idle and low engine RPM to cool the engine properly.
When possible, use a thermostatically controlled fan clutch. While a thermostatically modulated fan clutch is an effective means of operating the cooling system's fan, a worn or defective fan clutch can cause overheating if left undiagnosed. Sometimes they may appear to be OK when cold but they will free-wheel when hot.
Water pump and crankshaft pulleys sized according to what was on the engine from the factory. On a street motor, shoot for 1.2 to 1.3 times crank speed for pump pulley speed. This is usually true until you get to 3.55 gears and numerically higher, then 1:1 works better. Most 1960s muscle cars are 1:1. Sustained pump speeds over 4200 rpm can cause cavitation. Race vehicles may use a 2.3:1 ratio for a 9000-plus rpm engine.
On a carburetor-equipped engine, often a 180º thermostat is used, although a little hotter thermostat rating (190º-195º) may make the motor more responsive and add a little fuel mileage. It may also help to burn off some of the by-products of combustion, such as moisture and acids which form and get into the oil. Motors using EFI induction should use the thermostat temperature specified by the factory for that particular motor to prevent false input to the computer and consequent problems. The sensor pill goes toward the motor.
Use a spiral-wound spring in the bottom radiator hose, to prevent collapse of the hose.
Use the proper pressure cap for the radiator being used.
Ensure that there is adequate airflow from the engine compartment to allow the exit of the air drawn into the compartment. In custom applications this might require the removal or surgery of inner fender panels or using spacers to raise the hood of the car up an inch or two at the back.
Maintain the proper coolant/water mix to prevent freezing up in winter. Water transfers heat better than coolant, but some coolant must be used to prevent freezing. Using a 50/50 mix of coolant/water is a necessity for motors using aluminum parts. Plain water will turn aluminum into oatmeal.
Before installing the water pump, grasp the impeller with one hand and the drive hub with the other and twist to make sure the impeller is tight on the drive shaft. Not finding this problem beforehand can cause damage.
Although it may not be necessary, the concept of a "water pump conversion disc" can be researched. Flow Kooler originally marketed flat aluminum discs to be riveted to the backside of the stamped steel impeller of the water pump. With an iron impeller, a steel disc could be welded or brazed onto the impeller. Such a disc wouldn't be that difficult to make. Space the water pump backing plate back farther with a couple of gaskets to prevent interference of the rivet heads on the backing plate if riveting a disc to a stamped steel impeller. More info: brazing cast iron, Flow Kooler water pump conversion discs. This disc could make an appreciable difference in the flow of water at engine speeds under 3,000 RPM. On the other hand, Howard Stewart of Stewart Components (the guy with the water pump dyno), says that these discs have little to no effect.....
........ Coolant
Sometimes the key to a bulletproof system is what you put in it and how. You can't just open the radiator cap and dump anything in it. A 50/50 mix of water and ethylene glycol antifreeze boils at 225º if there is no pressure like when the radiator cap is open or defective. But if the cooling system is sealed and will hold pressure, a radiator cap rated at 15 psi will increase the boiling point of a 50/50 coolant mix to 265º. If the ratio of antifreeze to water is increased to 70/30 (the maximum recommended), the boiling point under 15 psi of pressure increases to 276º.
Water is the basis of coolant in most systems. Can the water that you start with have a detrimental effect on your cooling system? Yes! Water is not necessarily clean and free from contaminants. Water can contain acid, alkaline, foreign matter, etc. These contaminants can combine with the metal within the cooling system and contribute to plugging or slowing down the flow within the system. Today, you will find about 10 different antifreeze products and about 30 different additives for your cooling system. WHY do you need them? Good question!
Engineers have come up with cooling system recommendations based on their extensive research and their recommendations and warnings should be heeded. Your OEM dealer and manufacturer usually recommend using a 50/50 mix of antifreeze and water. This is to protect and prolong the life of cooling system metals and seals. Using unapproved additives or incorrect chemicals or ratios, etc., could be harmful to the cooling system and could also result in needless repair and expense.
There are additives of all sorts on the market. WaterWetter is one. John Deere Cool-Gard II is another. Note that tap water is sometimes not very good as it can contain minerals.
When you are refilling your cooling system, the radiator cap is open, and you pour directly into the system until it is full. "Full" means a level one inch less than the cap height. The engine should be warmed up and running at a fast idle of 1000 to 1200 rpm's. The engine is run until you can see movement in the radiator and a slight steam rises from the open cap outlet. If you have a gauge, verify that the temperature is at operating temperate of 160º to 195º. The cap is placed on the radiator outlet and turned until tight with the arrows aligned to point at the overflow outlet. The overflow bottle should be within its limits, which is usually marked on the container walls.
When you are adding to the system, do not open the radiator cap. Instead, add directly to the reservoir tank.
If you have ever watched a pot of water start to boil on the stove, you will know that tiny air bubbles start to rise from the bottom of the pot as the heat is raised. Adding a water 'conditioner' like WaterWetter to your coolant will break the surface tension and provide a greater contact area for the coolant. A wetting additive can supposedly decrease the temperature up to 20º F.
On a closed system with an overflow bottle, that the system should be filled to the top when it is at operating temperature. One of the advantages of this type of system is to reduce oxidation by eliminating all air from the system. Hence it then becomes a closed system. Why leave a head of air in the top of the radiator when you don't have to? Entrained air is sometimes difficult to get out of the system. The secret in the system lies in the overflow bottle. Coolant expands with heat, thus increasing the total water volume mass. When the pressure increase exceeds the radiator cap's capacity, the coolant passes from the radiator to the overflow bottle which is vented to the atmosphere. When the mass is cooled due to the air flow through the radiator or turning off the engine, the radiator cap will allow the coolant to be syphoned from the overflow tank back into the radiator/cooling system, thus keeping a set amount of mass present in the cooling system.
Radiator shroud
Radiator shrouds are devices that control the exiting air from the radiator and direct it to a rearward sucking electric or mechanical fan. Shrouds can be made from plastic, fiberglass, and metal (aluminum or steel). They cover the rear portion of the radiator. Allow air passing through the radiator to be ducted to the fan which directs air flow over the engine and out of the engine bay. In most cases, the mechanical fan will be inserted approximately 1/3 of the depth of the fan blades into the shroud, this is usually sufficient to draw a full charge of air and disburse it adequately without disrupting air flow.
Radiator cap
A radiator cap is important to the proper operation of the entire cooling system. The cap is designed to hold pressure in the system. Under pressure the coolant boils at a higher temperature than when non pressurized (approximately 3º per 1 psi) so a 10 psi cap will add 30º to the boiling point of the coolant. Check the cap gasket for cracks and other damage. If the cap pressure spring is badly rusted replace the cap, observing the pressure stamped on the old unit, acquire one with the same pressure rating. During inspection make sure that the radiator filler neck (where the cap lives) is clean and the sealing surfaces are undamaged.
A radiator with a nicked or damaged sealing surface can be repaired by employing a metal filled epoxy to fill the imperfections. Recommended steps:
Sand the sealing surface to bright metal
Clean the sealing area with water
Dry thoroughly
Mix the metal filled epoxy following manufacturer’s directions
Apply a thin bead on the sealing surface
Using a plastic implement smooth the bead covering damage and imperfections. Make sure the epoxy is smooth and even.
Let harden, install cap.
Note: This technique has been used on GM, VW and Porsche radiators to good effect.
Thermostat
The thermostat has two important jobs to perform; to accelerate engine warm-up and to regulate the engine's operating temperature. A quality thermostat ensures excellent fuel economy, reduces engine wear, diminishes emissions and blow-by, improves cold weather drivability, provides adequate heater output, and deters overheating. This is accomplished by blocking the circulation of coolant between the engine and radiator until the engine has reached its predetermined temperature. The thermostat then opens as required in response to changes in coolant temperature to keep the engine's temperature within the desired operating range.
Thermostats have a “rated” temperature such as 180º F or 195º F. This is the temperature the thermostat will start to open, give or take 3º.
Usually located within a metal or plastic housing where the upper radiator hose connects to the engine, most of today’s thermostats utilize the "reverse poppet" design, which opens against the flow of the coolant. Thermostats have a wax filled copper housing or cup called a "heat motor" that pushes the thermostat open against spring pressure.
As the engine's coolant warms up, the increase in heat causes the wax to melt and expand. The wax pushes against a piston inside a rubber boot. This forces the piston outward to open the thermostat. Within 3º or 4º F. of the thermostat preset/rated temperature which is usually marked on the thermostat, the thermostat begins to unseat so coolant can start to circulate between the engine and radiator. It continues to open until engine cooling requirements are satisfied. It is fully open about 15º-20º above its rated temperature. If the temperature of the circulating coolant begins to drop, the wax element contracts, allowing spring tension to close the thermostat, thus decreasing coolant flow through the radiator.
On some applications, the thermostat performs an additional function. It closes off a bypass circuit inside the engine when it opens the radiator circuit. The bypass circuit circulates coolant inside the engine so that hot spots can’t form when the radiator circuit is closed.
Many thermostats have a “jiggle pin” that allows trapped air in the cooling system to pass through the thermostat and be removed from the system. If a Stant thermostat does not have a jiggle pin, it will have a "bleed notch” or other method of removing air from the system.
Thermostat failures
There is no such thing as a thermostat that will fail in a “safe” position. All thermostats will fail in either a closed or open position. One brand claims it fails in a safe position, but it simply locks itself open when it is a full stroke open position. It will not spring open if it fails in a closed position.
A thermostat fails “open” if the return spring breaks or debris prevents the thermostat valve from fully seating or closing. In this instance the thermostat allows continuous coolant flow to the radiator; therefore, the engine will be overcooled. The tangible effects are poor warm up and heater performance, increased engine emissions and reduced fuel economy. For these reasons, an engine should never be operated without a thermostat in place, even in extreme temperatures.
A thermostat will fail “closed” if the wax element has been damaged by overheating (from loss of coolant, a defective electric cooling fan or fan clutch) or corrosion (from not changing the anti-freeze often enough). This failure prevents the flow of coolant to the radiator; therefore, the engine will be overheated. The tangible effects are a boil over, the inability to operate the vehicle, and the likelihood of severe engine damage. For these reasons alone, when an engine overheats, it’s a good idea to replace the thermostat whether it caused the problem or not.
[edit] Replacement thermostats
The temperature rating of a replacement thermostat must be the correct one for the application because of the adverse effects the wrong thermostat can have on drivability, engine performance and emissions.
The temperature rating specified by the car manufacturer is especially important in many 1981 and newer vehicles because the on-board computer monitors coolant temperature through a coolant sensor to control fuel enrichment, spark timing and operation of the EGR valve. Even on vehicles without computers, thermal vacuum switches that react to a specific coolant temperature are often used to open and close various vacuum circuits that regulate fuel enrichment, timing and EGR. If a colder thermostat is installed, the coolant may never get hot enough to trigger the appropriate control functions or to allow a computer system to go into “closed loop”. Too hot a thermostat can also interfere with the proper operation of engine controls, and increase the engine’s operating temperature to the point where it may experience detonation (spark knock).
[edit] Thermostat checks
One way to determine if the thermostat is doing its job is to feel the upper radiator hose after starting a cold engine. The hose should not feel hot until the engine has warmed up. If the hose starts to feel hot after only a couple of minutes, the thermostat may be stuck open or not closing completely. Once the engine is warm, the hose should feel hot as coolant circulates between the engine and radiator. If the hose does not feel hot, the thermostat may be stuck shut, blocking the flow of coolant.
A thermostat can be tested by suspending it, using a string through the valve, in a bucket of boiling 50/50 coolant and water. If the thermostat is working it will fall off the string as it starts to open after being in the hot/boiling coolant for a few minutes. When removed and allowed to cool, the thermostat should close.
[edit] Replacement tips
Don't overlook the water outlet covering the thermostat. Check for cracks, broken flanges, internal pitting and corrosion, and erosion at the hose neck (a real problem with most aluminum housings). The gasket surface must be flat and free from warping or deep scratches.
Scrape the mating surfaces on the thermostat housing and engine to remove all traces of old gasket material. Use care on aluminum because the soft metal can be easily scratched.
Temporarily stuffing a clean rag into the thermostat opening on the engine while the housing is removed helps keep debris out of the cooling system.
Install the new thermostat so the copper heat sensing element is toward the engine. If installed upside down, it won’t open.
Torque the thermostat housing bolts evenly and to the manufacturer's recommendations.
To insure air has been removed from the cooling system after replacing a thermostat, be sure to run the engine a few minutes, let it cool, and refill the antifreeze as needed.
NOTE: The old type of thermostat used metal bellows filled with a liquid. The condensed liquid would "suck" the bellows closed. This type of thermostat always fails in the open position which is extremely convenient as one does not have to buy a new cylinder head or engine. Nowadays this type is very difficult to obtain.
While doing some research on an overheating problem, I came across this Wiki with loads of useful information on how your cooling system.
http://www.crankshaftcoalition.com/wiki/Bulletproof_cooling_system
It's very informative on how your cooling system works, the different components to it and how they are all related. Easy to read, easy to comprehend and apply to almost any cooling problem you may have.
*note - it's not written specifically for Diesel vehicles, but it applies to almost any vehicle. Also, all units quoted are in Farenheit.
Some snippets from the site:
How the cooling system works
Note- All temperatures are in degrees Fahrenheit.
The cooling system works by absorbing, transporting, and dissipating heat. Therefore, anything that impedes any of those functions can cause overheating:
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.
The 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.
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.
Overheating and its causes
"Overheating" essentially just means that the cooling system is taking on more heat than it can dissipate. 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.
Overheating can be caused by anything that decreases the cooling system’s ability to absorb, transport and dissipate heat. Some causes of overheating are:
Low coolant level, loss of coolant, or insufficient coolant capacity
Buildup of deposits that cause poor conduction of heat into the cooling system
A thermostat that won't open
Poor airflow through the radiator
Damaged or worn fan clutch, or broken fan
Collapsed radiator hose
Loose or defective water pump impeller
Defective radiator cap
Late ignition timing
Bulletproof cooling system tips
Clogging and leaks are two of the most common radiator problems. Bugs, dirt, and debris can block airflow, and limit the radiator's heat-dissipating characteristics. Thus, it's recommended to "back flush" the radiator and cooling system when changing coolant. This helps to clean out deposits, and flushes the remaining coolant from the engine block. You can back flush the radiator by running water through it in the opposite direction of regular flow. Typically, after draining the radiator a t-fitting can be installed in the heater inlet hose. This fitting gets connected to a pressurized water hose, and the system is reverse flushed. Do this until clean water emerges.
A rough guide is to use a radiator at least as large as the one that was originally used to cool the engine, with the same or more radiator cores. However, it's important to note that additional rows don't add a proportional amount of cooling, i.e. a 3-row radiator does not necessarily offer 50% more cooling than a 2-row radiator. This is because subsequent rows receive warm air from the rows in front of them. However, adding radiator frontal area IS proportional, but this usually causes fitment issues, so additional rows are generally the only viable choice. Also the radiator design and materials can have an effect on the radiator efficiency; a larger radiator is not necessarily a better radiator.
Oftentimes, the cheapest and most bulletproof way is to use the largest radiator that will fit, along with the fan type and size, and shroud that was designed for the radiator from the factory.
Use a full shroud, with the radiator positioned so that the fan blades are half-in and half-out of the shroud hole, and no more than 1" of clearance between the shroud and the fan blade tips (just enough to prevent interference when the motor rocks on its rubber mounts).
Fan recommendations: OEM 18 inch, 7-blade steel fan with 2" to 2-3/4" pitch. The pitch of a fan can be measured by laying the fan down on a flat surface and measuring from the flat surface to the edge of the fan blade. Fans that are relatively flat (such as a flex fan) may not move enough air at idle and low engine RPM to cool the engine properly.
When possible, use a thermostatically controlled fan clutch. While a thermostatically modulated fan clutch is an effective means of operating the cooling system's fan, a worn or defective fan clutch can cause overheating if left undiagnosed. Sometimes they may appear to be OK when cold but they will free-wheel when hot.
Water pump and crankshaft pulleys sized according to what was on the engine from the factory. On a street motor, shoot for 1.2 to 1.3 times crank speed for pump pulley speed. This is usually true until you get to 3.55 gears and numerically higher, then 1:1 works better. Most 1960s muscle cars are 1:1. Sustained pump speeds over 4200 rpm can cause cavitation. Race vehicles may use a 2.3:1 ratio for a 9000-plus rpm engine.
On a carburetor-equipped engine, often a 180º thermostat is used, although a little hotter thermostat rating (190º-195º) may make the motor more responsive and add a little fuel mileage. It may also help to burn off some of the by-products of combustion, such as moisture and acids which form and get into the oil. Motors using EFI induction should use the thermostat temperature specified by the factory for that particular motor to prevent false input to the computer and consequent problems. The sensor pill goes toward the motor.
Use a spiral-wound spring in the bottom radiator hose, to prevent collapse of the hose.
Use the proper pressure cap for the radiator being used.
Ensure that there is adequate airflow from the engine compartment to allow the exit of the air drawn into the compartment. In custom applications this might require the removal or surgery of inner fender panels or using spacers to raise the hood of the car up an inch or two at the back.
Maintain the proper coolant/water mix to prevent freezing up in winter. Water transfers heat better than coolant, but some coolant must be used to prevent freezing. Using a 50/50 mix of coolant/water is a necessity for motors using aluminum parts. Plain water will turn aluminum into oatmeal.
Before installing the water pump, grasp the impeller with one hand and the drive hub with the other and twist to make sure the impeller is tight on the drive shaft. Not finding this problem beforehand can cause damage.
Although it may not be necessary, the concept of a "water pump conversion disc" can be researched. Flow Kooler originally marketed flat aluminum discs to be riveted to the backside of the stamped steel impeller of the water pump. With an iron impeller, a steel disc could be welded or brazed onto the impeller. Such a disc wouldn't be that difficult to make. Space the water pump backing plate back farther with a couple of gaskets to prevent interference of the rivet heads on the backing plate if riveting a disc to a stamped steel impeller. More info: brazing cast iron, Flow Kooler water pump conversion discs. This disc could make an appreciable difference in the flow of water at engine speeds under 3,000 RPM. On the other hand, Howard Stewart of Stewart Components (the guy with the water pump dyno), says that these discs have little to no effect.....
........ Coolant
Sometimes the key to a bulletproof system is what you put in it and how. You can't just open the radiator cap and dump anything in it. A 50/50 mix of water and ethylene glycol antifreeze boils at 225º if there is no pressure like when the radiator cap is open or defective. But if the cooling system is sealed and will hold pressure, a radiator cap rated at 15 psi will increase the boiling point of a 50/50 coolant mix to 265º. If the ratio of antifreeze to water is increased to 70/30 (the maximum recommended), the boiling point under 15 psi of pressure increases to 276º.
Water is the basis of coolant in most systems. Can the water that you start with have a detrimental effect on your cooling system? Yes! Water is not necessarily clean and free from contaminants. Water can contain acid, alkaline, foreign matter, etc. These contaminants can combine with the metal within the cooling system and contribute to plugging or slowing down the flow within the system. Today, you will find about 10 different antifreeze products and about 30 different additives for your cooling system. WHY do you need them? Good question!
Engineers have come up with cooling system recommendations based on their extensive research and their recommendations and warnings should be heeded. Your OEM dealer and manufacturer usually recommend using a 50/50 mix of antifreeze and water. This is to protect and prolong the life of cooling system metals and seals. Using unapproved additives or incorrect chemicals or ratios, etc., could be harmful to the cooling system and could also result in needless repair and expense.
There are additives of all sorts on the market. WaterWetter is one. John Deere Cool-Gard II is another. Note that tap water is sometimes not very good as it can contain minerals.
When you are refilling your cooling system, the radiator cap is open, and you pour directly into the system until it is full. "Full" means a level one inch less than the cap height. The engine should be warmed up and running at a fast idle of 1000 to 1200 rpm's. The engine is run until you can see movement in the radiator and a slight steam rises from the open cap outlet. If you have a gauge, verify that the temperature is at operating temperate of 160º to 195º. The cap is placed on the radiator outlet and turned until tight with the arrows aligned to point at the overflow outlet. The overflow bottle should be within its limits, which is usually marked on the container walls.
When you are adding to the system, do not open the radiator cap. Instead, add directly to the reservoir tank.
If you have ever watched a pot of water start to boil on the stove, you will know that tiny air bubbles start to rise from the bottom of the pot as the heat is raised. Adding a water 'conditioner' like WaterWetter to your coolant will break the surface tension and provide a greater contact area for the coolant. A wetting additive can supposedly decrease the temperature up to 20º F.
On a closed system with an overflow bottle, that the system should be filled to the top when it is at operating temperature. One of the advantages of this type of system is to reduce oxidation by eliminating all air from the system. Hence it then becomes a closed system. Why leave a head of air in the top of the radiator when you don't have to? Entrained air is sometimes difficult to get out of the system. The secret in the system lies in the overflow bottle. Coolant expands with heat, thus increasing the total water volume mass. When the pressure increase exceeds the radiator cap's capacity, the coolant passes from the radiator to the overflow bottle which is vented to the atmosphere. When the mass is cooled due to the air flow through the radiator or turning off the engine, the radiator cap will allow the coolant to be syphoned from the overflow tank back into the radiator/cooling system, thus keeping a set amount of mass present in the cooling system.
Radiator shroud
Radiator shrouds are devices that control the exiting air from the radiator and direct it to a rearward sucking electric or mechanical fan. Shrouds can be made from plastic, fiberglass, and metal (aluminum or steel). They cover the rear portion of the radiator. Allow air passing through the radiator to be ducted to the fan which directs air flow over the engine and out of the engine bay. In most cases, the mechanical fan will be inserted approximately 1/3 of the depth of the fan blades into the shroud, this is usually sufficient to draw a full charge of air and disburse it adequately without disrupting air flow.
Radiator cap
A radiator cap is important to the proper operation of the entire cooling system. The cap is designed to hold pressure in the system. Under pressure the coolant boils at a higher temperature than when non pressurized (approximately 3º per 1 psi) so a 10 psi cap will add 30º to the boiling point of the coolant. Check the cap gasket for cracks and other damage. If the cap pressure spring is badly rusted replace the cap, observing the pressure stamped on the old unit, acquire one with the same pressure rating. During inspection make sure that the radiator filler neck (where the cap lives) is clean and the sealing surfaces are undamaged.
A radiator with a nicked or damaged sealing surface can be repaired by employing a metal filled epoxy to fill the imperfections. Recommended steps:
Sand the sealing surface to bright metal
Clean the sealing area with water
Dry thoroughly
Mix the metal filled epoxy following manufacturer’s directions
Apply a thin bead on the sealing surface
Using a plastic implement smooth the bead covering damage and imperfections. Make sure the epoxy is smooth and even.
Let harden, install cap.
Note: This technique has been used on GM, VW and Porsche radiators to good effect.
Thermostat
The thermostat has two important jobs to perform; to accelerate engine warm-up and to regulate the engine's operating temperature. A quality thermostat ensures excellent fuel economy, reduces engine wear, diminishes emissions and blow-by, improves cold weather drivability, provides adequate heater output, and deters overheating. This is accomplished by blocking the circulation of coolant between the engine and radiator until the engine has reached its predetermined temperature. The thermostat then opens as required in response to changes in coolant temperature to keep the engine's temperature within the desired operating range.
Thermostats have a “rated” temperature such as 180º F or 195º F. This is the temperature the thermostat will start to open, give or take 3º.
Usually located within a metal or plastic housing where the upper radiator hose connects to the engine, most of today’s thermostats utilize the "reverse poppet" design, which opens against the flow of the coolant. Thermostats have a wax filled copper housing or cup called a "heat motor" that pushes the thermostat open against spring pressure.
As the engine's coolant warms up, the increase in heat causes the wax to melt and expand. The wax pushes against a piston inside a rubber boot. This forces the piston outward to open the thermostat. Within 3º or 4º F. of the thermostat preset/rated temperature which is usually marked on the thermostat, the thermostat begins to unseat so coolant can start to circulate between the engine and radiator. It continues to open until engine cooling requirements are satisfied. It is fully open about 15º-20º above its rated temperature. If the temperature of the circulating coolant begins to drop, the wax element contracts, allowing spring tension to close the thermostat, thus decreasing coolant flow through the radiator.
On some applications, the thermostat performs an additional function. It closes off a bypass circuit inside the engine when it opens the radiator circuit. The bypass circuit circulates coolant inside the engine so that hot spots can’t form when the radiator circuit is closed.
Many thermostats have a “jiggle pin” that allows trapped air in the cooling system to pass through the thermostat and be removed from the system. If a Stant thermostat does not have a jiggle pin, it will have a "bleed notch” or other method of removing air from the system.
Thermostat failures
There is no such thing as a thermostat that will fail in a “safe” position. All thermostats will fail in either a closed or open position. One brand claims it fails in a safe position, but it simply locks itself open when it is a full stroke open position. It will not spring open if it fails in a closed position.
A thermostat fails “open” if the return spring breaks or debris prevents the thermostat valve from fully seating or closing. In this instance the thermostat allows continuous coolant flow to the radiator; therefore, the engine will be overcooled. The tangible effects are poor warm up and heater performance, increased engine emissions and reduced fuel economy. For these reasons, an engine should never be operated without a thermostat in place, even in extreme temperatures.
A thermostat will fail “closed” if the wax element has been damaged by overheating (from loss of coolant, a defective electric cooling fan or fan clutch) or corrosion (from not changing the anti-freeze often enough). This failure prevents the flow of coolant to the radiator; therefore, the engine will be overheated. The tangible effects are a boil over, the inability to operate the vehicle, and the likelihood of severe engine damage. For these reasons alone, when an engine overheats, it’s a good idea to replace the thermostat whether it caused the problem or not.
[edit] Replacement thermostats
The temperature rating of a replacement thermostat must be the correct one for the application because of the adverse effects the wrong thermostat can have on drivability, engine performance and emissions.
The temperature rating specified by the car manufacturer is especially important in many 1981 and newer vehicles because the on-board computer monitors coolant temperature through a coolant sensor to control fuel enrichment, spark timing and operation of the EGR valve. Even on vehicles without computers, thermal vacuum switches that react to a specific coolant temperature are often used to open and close various vacuum circuits that regulate fuel enrichment, timing and EGR. If a colder thermostat is installed, the coolant may never get hot enough to trigger the appropriate control functions or to allow a computer system to go into “closed loop”. Too hot a thermostat can also interfere with the proper operation of engine controls, and increase the engine’s operating temperature to the point where it may experience detonation (spark knock).
[edit] Thermostat checks
One way to determine if the thermostat is doing its job is to feel the upper radiator hose after starting a cold engine. The hose should not feel hot until the engine has warmed up. If the hose starts to feel hot after only a couple of minutes, the thermostat may be stuck open or not closing completely. Once the engine is warm, the hose should feel hot as coolant circulates between the engine and radiator. If the hose does not feel hot, the thermostat may be stuck shut, blocking the flow of coolant.
A thermostat can be tested by suspending it, using a string through the valve, in a bucket of boiling 50/50 coolant and water. If the thermostat is working it will fall off the string as it starts to open after being in the hot/boiling coolant for a few minutes. When removed and allowed to cool, the thermostat should close.
[edit] Replacement tips
Don't overlook the water outlet covering the thermostat. Check for cracks, broken flanges, internal pitting and corrosion, and erosion at the hose neck (a real problem with most aluminum housings). The gasket surface must be flat and free from warping or deep scratches.
Scrape the mating surfaces on the thermostat housing and engine to remove all traces of old gasket material. Use care on aluminum because the soft metal can be easily scratched.
Temporarily stuffing a clean rag into the thermostat opening on the engine while the housing is removed helps keep debris out of the cooling system.
Install the new thermostat so the copper heat sensing element is toward the engine. If installed upside down, it won’t open.
Torque the thermostat housing bolts evenly and to the manufacturer's recommendations.
To insure air has been removed from the cooling system after replacing a thermostat, be sure to run the engine a few minutes, let it cool, and refill the antifreeze as needed.
NOTE: The old type of thermostat used metal bellows filled with a liquid. The condensed liquid would "suck" the bellows closed. This type of thermostat always fails in the open position which is extremely convenient as one does not have to buy a new cylinder head or engine. Nowadays this type is very difficult to obtain.
