Bulletproof cooling system

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*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).
 
*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.  
 
*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.  
*Thermostatically controlled fan clutch.
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*When possible, use a thermostatically controlled fan clutch. Note, 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.
 
*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, most of us use a 180º thermostat, although a little hotter thermostat (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.
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*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 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.
 
*Use the proper pressure cap for the radiator being used.
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*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.
 
*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: [http://www.smokstak.com/forum/showthread.php?t=11774 brazing cast iron], [http://store.summitracing.com/partdetail.asp?part=BRA%2D4375%2D07&autoview=sku 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.
 
*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: [http://www.smokstak.com/forum/showthread.php?t=11774 brazing cast iron], [http://store.summitracing.com/partdetail.asp?part=BRA%2D4375%2D07&autoview=sku 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.
 
'''NOTE:''' 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.
 
  
 
==Swapping a core support and matching radiator into a recipient vehicle==
 
==Swapping a core support and matching radiator into a recipient vehicle==
 
In doing this swap, you will have to re-install the recipient vehicle's hood latch onto the donor core support in the proper location. Make up a fixture beforehand from scrap metal that bolts to the fender bolts or some other location that will be the same after the core support swap, and will show the proper location for the latch. This is a must-do when doing a frame or clip swap.
 
In doing this swap, you will have to re-install the recipient vehicle's hood latch onto the donor core support in the proper location. Make up a fixture beforehand from scrap metal that bolts to the fender bolts or some other location that will be the same after the core support swap, and will show the proper location for the latch. This is a must-do when doing a frame or clip swap.
 
===Recommended donor vehicles===
 
*1976 Cadillac Fleetwood or Eldorado. For example: [http://www.radiatorexpress.com/product.asp?part=1976+CADILLAC+FLEETWOOD++%2D+8%2E2+liter+V8+RADIATOR+Name+Brand+Replacement&part_id=1357&aaia_id=1026582 1976 Cadillac Fleetwood 8.2 liter V8 radiator].
 
*Mid-70's Chevrolet truck with a 454. For example: [http://www.radiatorexpress.com/product.asp?part=1975+CHEVROLET+C20+PICKUP++%2D+7%2E4+liter+V8+RADIATOR+Name+Brand+4%2DRow+Capacity+Upgrade+%2828%22x19%22%29&part_id=39583&aaia_id=1031971 1975 Chevrolet C20 Pickup - 7.4 liter V8 radiator, 4-row capacity upgrade] (and, same radiator in aluminum: [http://www.radiatorexpress.com/product.asp?part=1975+CHEVROLET+C20+PICKUP++%2D+7%2E4+liter+V8+RADIATOR+All+Aluminum+4%2DRow+Capacity+%2828%22X19%22%29&part_id=218171&aaia_id=1031971 here]).
 
  
 
====Cadillac radiator swap====
 
====Cadillac radiator swap====
 
Any of the Fleetwood or Eldorado Caddy’s from '70 to '76 with a 472 or 500 will work.
 
Any of the Fleetwood or Eldorado Caddy’s from '70 to '76 with a 472 or 500 will work.
  
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===Examples of donor vehicles===
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*1976 Cadillac Fleetwood or Eldorado. For example: [http://www.radiatorexpress.com/product.asp?part=1976+CADILLAC+FLEETWOOD++%2D+8%2E2+liter+V8+RADIATOR+Name+Brand+Replacement&part_id=1357&aaia_id=1026582 1976 Cadillac Fleetwood 8.2 liter V8 radiator].
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*Mid-70's Chevrolet truck with a 454. For example: [http://www.radiatorexpress.com/product.asp?part=1975+CHEVROLET+C20+PICKUP++%2D+7%2E4+liter+V8+RADIATOR+Name+Brand+4%2DRow+Capacity+Upgrade+%2828%22x19%22%29&part_id=39583&aaia_id=1031971 1975 Chevrolet C20 Pickup - 7.4 liter V8 radiator, 4-row capacity upgrade] (and, same radiator in aluminum: [http://www.radiatorexpress.com/product.asp?part=1975+CHEVROLET+C20+PICKUP++%2D+7%2E4+liter+V8+RADIATOR+All+Aluminum+4%2DRow+Capacity+%2828%22X19%22%29&part_id=218171&aaia_id=1031971 here]).
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===Swap procedure===
 
Call around and find a boneyard that still has the fan, shroud and core support. You'll be using a new radiator and viscous drive fan clutch to bulletproof your installation. Make yourself a memo of the exact year and model the pieces came from so you can match up the parts.
 
Call around and find a boneyard that still has the fan, shroud and core support. You'll be using a new radiator and viscous drive fan clutch to bulletproof your installation. Make yourself a memo of the exact year and model the pieces came from so you can match up the parts.
  
 
You may or may not have to alter the fan clutch hub where it bolts to the water pump/pulley. Usually, the holes are slotted so you can make it work. If not, some minor surgery on the hub with a rat-tail file will do the trick. With the motor in the vehicle and finalized for position, bolt the fan clutch and fan to the water pump. Mount the Cadillac radiator and shroud to the Cadillac core support.
 
You may or may not have to alter the fan clutch hub where it bolts to the water pump/pulley. Usually, the holes are slotted so you can make it work. If not, some minor surgery on the hub with a rat-tail file will do the trick. With the motor in the vehicle and finalized for position, bolt the fan clutch and fan to the water pump. Mount the Cadillac radiator and shroud to the Cadillac core support.
  
The Cadillac core support will probably be longer side to side than the stock one in the recipient vehicle. Retain the outer pieces of the recipient vehicle support where it bolts into the body and cut the middle part of the recipient vehicle support out with a reciprocating saw, leaving a few inches on each side. Then, measure the opening between the two stubs that are still bolted to the recipient vehicle and cut the Cadillac support to fit into this opening. It's better to leave a little more sheet metal on the Cadillac support until you determine the correct position of the fan where it engages the shroud opening. Then, position the Cadillac support with radiator and shroud attached up to the fan, equalizing the distance between the fan blade tips and the inner circumference of the shroud all around. Move the shroud around the fan until you have the fan blades halfway in and halfway out of the shroud opening. Normally, you'll have to tilt the top of the radiator/shroud back a little at the top to match the fan angle because the motor sits in the recipient vehicle on a rearward tilt. If you need a little more front to rear clearance for mounting the support, you can position the fan blades half in and half out of the shroud opening. A little further in is OK, as long as the fan clutch is at least 1" from the radiator core material. A little further out is not OK.
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The Cadillac core support will probably be longer side to side than the stock one in the recipient vehicle. Retain the outer pieces of the recipient vehicle support where it bolts into the body and cut the middle part of the recipient vehicle support out with a reciprocating saw, leaving a few inches on each side. Then, measure the opening between the two stubs that are still bolted to the recipient vehicle and cut the Cadillac support to fit into this opening. It's better to leave a little more sheet metal on the Cadillac support until you determine the correct position of the fan where it engages the shroud opening.  
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Then, position the Cadillac support with radiator and shroud attached up to the fan, equalizing the distance between the fan blade tips and the inner circumference of the shroud all around. Move the shroud around the fan until you have the fan blades halfway in and halfway out of the shroud opening. Normally, you'll have to tilt the top of the radiator/shroud back a little at the top to match the fan angle because the motor sits in the recipient vehicle with a rearward tilt. If you need a little more front to rear clearance for mounting the support, you can position the fan blades a little further in, as long as the fan clutch is at least 1" from the radiator core material. A little further out should be avoided if possible.
  
 
With that accomplished, simply attach the middle piece of the Cadillac support to the stubs of the recipient vehicle support. Use whatever pieces of sheet metal or whatever that you have to in order to make the connection. The Cadillac support may end up sitting forward of the stubs or a little behind them or it might fall exactly into place and you'll have very little welding to do to stitch the Cad support and the stubs together. Whatever. Just use your head and figure out how to connect the sheet metal, then MIG it in place.
 
With that accomplished, simply attach the middle piece of the Cadillac support to the stubs of the recipient vehicle support. Use whatever pieces of sheet metal or whatever that you have to in order to make the connection. The Cadillac support may end up sitting forward of the stubs or a little behind them or it might fall exactly into place and you'll have very little welding to do to stitch the Cad support and the stubs together. Whatever. Just use your head and figure out how to connect the sheet metal, then MIG it in place.
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The location of the pump is important. Some vehicles have been built with high mounted water pumps which have been a disaster.  In the case of a vehicle which has its engine mounted north-south, the water pump will often become the highest component in the cooling circuit when the vehicle is ascending a steep hill. Engine designers ought to study “steam trapping” and “air venting” as it is a very important topic even for things that do not run on steam.
 
The location of the pump is important. Some vehicles have been built with high mounted water pumps which have been a disaster.  In the case of a vehicle which has its engine mounted north-south, the water pump will often become the highest component in the cooling circuit when the vehicle is ascending a steep hill. Engine designers ought to study “steam trapping” and “air venting” as it is a very important topic even for things that do not run on steam.
  
With a transverse engine vehicle it is possible to have the water pump behind the engine block.  With this arrangement steep hills will not starve the pump of water. AVOID any car that relies on venting screws in its cooling system.
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With a transverse engine vehicle it is possible to have the water pump behind the engine block.  With this arrangement steep hills will not starve the pump of water.  
  
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[[file:Falcon_eng02.jpg|border|350px|Example of electric motor drive on OEM water pump]]<br style="clear:both"/>
  
[[file:Falcon_eng02.jpg|frame|none|Example of electric motor drive on OEM water pump]]
 
  
 
==Serpentine cross-flow radiators==
 
==Serpentine cross-flow radiators==
Most cars from 1960 and up used cross flow radiators. One of the reasons was a lower hoodline, and two, more cooling area was required to cool the larger engines. Cross flow radiators had a tank with an inlet/outlet placed on either side. The water entered on one side and passed through the core of the rad, was cooled by the air flow and the heat escaped through convection to the outside air. Engineers found that the longer the liquid was exposed to the cooling flow of air through the radiator core, the more heat could be extracted from the flowing water. They slowed down the water travel by increasing the size of the water pump pulleys, but that had its limitations. They also added more rows of core, but that too had limitations. Road course racers in 1969 found a way to keep cooling to a simple easy form. To do this, they pulled the tanks off the radiators that they were using and placed baffle plates in the tank covers. The baffles were placed so as to divide the radiator core section into three distinct areas. Water would enter the upper radiator inlet on the right side and would flow across the top section of the radiator to the left side, a baffle plate located 2/3 of the way down the tank caused the coolant to flow across the radiator to the right side to the right radiator tank. The coolant couldn't rise upwards because a baffle plate located 1/3 of the way down stopped it and forced it to head down lower in the right tank, where it again was drawn across the radiator core to the lower left tank outlet and out to the engine. This serpentine course that the coolant took allowed the coolant to be cooled THREE TIMES by the cooling air flow coming through the core area. "Excellent idea!" you say, “Why don't they do that to all cars today?” In a closed course environment, the theory works, but in real everyday life the average auto would never warm up to operating temperature during the daily commute.
 
 
Disagree, The Land Rover Discovery 300TDi (turbo diesel) had a crossflow radiator with the pipes at the same side.  Allegedly some radiators were faulty insofar as the baffle was not installed correctly so the water could go from input to output without going through the core.
 
 
[[Image:Cross_flow_radiators.gif|frame|Cross flow radiators.]]
 
[[Image:Cross_flow_radiators.gif|frame|Cross flow radiators.]]
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Most cars from 1960 and up used cross flow radiators. One of the reasons was a lower hoodline, and two, more cooling area was required to cool the larger engines. Cross flow radiators had a tank with an inlet/outlet placed on either side. The water entered on one side and passed through the core of the rad, was cooled by the air flow and the heat escaped through convection to the outside air. Engineers found that the longer the liquid was exposed to the cooling flow of air through the radiator core, the more heat could be extracted from the flowing water. They slowed down the water travel by increasing the size of the water pump pulleys, but that had its limitations. They also added more rows of core, but that too had limitations.
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Road course racers found a way to keep cooling to a simple easy form. To do this, they pulled the tanks off the radiators that they were using and placed baffle plates in the tank covers. The baffles were placed so as to divide the radiator core section into three distinct areas. Water would enter the upper radiator inlet on the right side and would flow across the top section of the radiator to the left side, a baffle plate located 2/3 of the way down the tank caused the coolant to flow across the radiator to the right side to the right radiator tank. The coolant couldn't rise upwards because a baffle plate located 1/3 of the way down stopped it and forced it to head down lower in the right tank, where it again was drawn across the radiator core to the lower left tank outlet and out to the engine. This serpentine course that the coolant took allowed the coolant to be cooled THREE TIMES by the cooling air flow coming through the core area. "Excellent idea!" you say, “Why don't they do that to all cars today?” In a closed course environment, the theory works, but in real everyday life the average auto might never warm up to operating temperature during the daily commute.
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==Does radiator tube size matter?==
 
==Does radiator tube size matter?==
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== Radiator shroud==
 
== 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 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==
 
== Radiator cap==
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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 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.
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A radiator with a nicked or damaged sealing surface can be repaired by employing a metal filled epoxy to fill the imperfections. Recommended steps:
 
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Recommended steps:
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* Sand the sealing surface to bright metal  
 
* Sand the sealing surface to bright metal  
 
* Clean the sealing area with water
 
* Clean the sealing area with water
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* Using a plastic implement smooth the bead covering damage and imperfections.  Make sure the epoxy is smooth and even.
 
* Using a plastic implement smooth the bead covering damage and imperfections.  Make sure the epoxy is smooth and even.
 
* Let harden, install cap.
 
* Let harden, install cap.
 
 
Note: This technique has been used on GM, VW and Porsche radiators to good effect.
 
Note: This technique has been used on GM, VW and Porsche radiators to good effect.
  
 
== Thermostat ==
 
== 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.
 
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.
  
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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.
 
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'''
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===Thermostat failures===
 
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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.
 
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.
  
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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.
 
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.
  
'''Replacement Thermostats'''
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===Replacement thermostats===
 
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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 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).
 
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).
  
'''Thermostat checks'''
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===Thermostat checks===
 
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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.
 
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.
 
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.
  
'''Replacement tips'''
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===Replacement tips===
 
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* 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.  
 
* 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.  
 
* 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.  
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* Torque the thermostat housing bolts evenly and to the manufacturer's recommendations.  
 
* 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.
 
* 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:''' Thermostat information courtesy of Stant, Inc.
 
For further information contact Chris Hoffman via email: choffman@stantinc.com. Via USPS: Chris Hoffman, 1620 Columbia Avenue Connersville, Indiana 47331-169. Via phone: 1-800-822-3121
 
  
 
'''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.
 
'''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.
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'''OIL COOLERS:'''
+
==Oil coolers==
 
+
 
Some cars will have the oil cooler installed in the radiator.  In the writers opinion this is an extremely bad idea as (1) Regarding cooling, one has all ones eggs in one basket.  (2) There is the risk of oil getting into the water or vice-versa.  Note that an oil-to-air heat exchanger is extremely difficult to boil and it is a reliable method of getting rid of waste heat.
 
Some cars will have the oil cooler installed in the radiator.  In the writers opinion this is an extremely bad idea as (1) Regarding cooling, one has all ones eggs in one basket.  (2) There is the risk of oil getting into the water or vice-versa.  Note that an oil-to-air heat exchanger is extremely difficult to boil and it is a reliable method of getting rid of waste heat.
  
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*[[Make a fiberglass fan shroud]]
 
*[[Make a fiberglass fan shroud]]
 
*[http://go.jeep-xj.info/HowtoRadiatorRestrictor.htm Using a restrictor washer in the system]
 
*[http://go.jeep-xj.info/HowtoRadiatorRestrictor.htm Using a restrictor washer in the system]
 
+
*Crankshaft Coalition wiki page [http://www.crankshaftcoalition.com/wiki/Thermostats_explained Thermostats explained]
 
==References==
 
==References==
 
*[http://www.aa1car.com/library/overheat.htm Engine overheating causes & cures]
 
*[http://www.aa1car.com/library/overheat.htm Engine overheating causes & cures]

Revision as of 13:20, 30 March 2012

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