Testing the Cooling System For leaks
The most common tool used to test a cooling system is the radiator pressure tester. A radiator pressure tester is really no more than a hand pump with a pressure gauge. The pressure tester is extremely handy for identifying the location of any leak within the cooling system. To use the tester, connect it to the radiator filler neck. Run the engine until it is warm, then pump the handle of the tester until its gauge reads the same pressure that is noted on the radiator cap. Watch the gauge. If the pressure drops, carefully check the hoses, radiator, heat Lore, and water pump for leaks. Often the leak will initially be obvious because coolant will spray out of the leak. If the pressure drops but there are no external leaks, suspect an internal leak.
Repairing Radiators
Most radiator leak repairs require the removal of the radiator from the vehicle. The coolant must be drained and all hoses and oil cooler lines disconnected. Bolts holding the radiator are then loosened and removed. The actual radiator repair procedures depend on the material of which it is made and the type of damage. Most radiator repairs are made by radiator specialty shops that employ technicians with knowledge of such work. If the
radiator is badly damaged, it should be replaced and the installation of a new one should be done as directed by the manufacturer. Many of today’s radiators have plastic tanks, which are not repaired. If these tanks leak, they are replaced.
PRESSURE CAP AND EXPANSION RESERVOIR
Radiator filler neck in modern use is covered with a pressure cap, which forms an air tight joint due to which the coolant is maintained at some pressure higher than the atmospheric. Due to this higher pressure the boiling point of coolant is raised. For approximately, 10 kpa increase in pressure, the boiling point is raised by 2.5°C. The following advantages thus result from the use of pressure cap ;
(i) The engine can operate at higher temperatures without boiling the coolant. As the rate of heat transfer from the cooling system to the atmosphere depends on the difference between coolant temperature and atmospheric temperature, this will result in additional heat transfer to the atmosphere. This means that for the same engine, a smaller radiator can be used.
(ii) The preparation of air-fuel mixture is improved at the higher operating temperatures.
(iii) with sealed cap, loss of coolant due to evaporation or surging is prevented, which makes the system particularly useful in deserts.
(iv) At high altitudes, the atmospheric pressure is low which causes the coolant to boil at a lower temperature. Thus under severe working conditions at high altitudes, e.g., during steep climb, the coolant in the radiator may boil if the system is open to atmosphere. with pressure cap, a higher pressure is maintained inside, irrespective of any change in the atmospheric pressure,
thus avoiding overhearing while driving at higher altitudes and thus maintaining the cooling efficiency of the system. A pressure cap. It contains a pressure valve and a vacuum valve. When due to severe working conditions, the coolant starts boiling and vaporises, the pressure in the system exceeds a certain predetermined value (50-100 kPa), the pressure blow-off valve opens
releasing the excess pressure to the atmosphere through the overflow pipe. on the -other hand if due to any reason (e.g. sudden cooling of the hot radiator), a vacuum is created inside, the vacuum valve operates to avoid collapse of the radiator. This valve is usually set to operate when the vacuum exceeds about 5 kPa. It is important to remember that a pressure cap should never be opened when the radiator is still hot, because on removing the cap, the pressure in the cooling system will suddenly drop, causing the boiling point of the coolant to be decreased all of a sudden. This causes the coolant to start boiling immediately, which may spill over and burn anyone standing nearby severely. Further, in case of loss of cap, the replacement cap must be of the same pressure rating as the original one. In some engines, instead of overflow pipe an expansion reservoir is provided. This is so connected with the radiator that it receives the excess coolant as the engine temperature increases, when the cooling water cools down, its volume decreases and the coolant in the reservoir returns to the radiator keeping the system full of coolant. The reservoir is usually made of translucent plastic so that it can indicate the level of the coolant anytime. such a system is also known as coolant recovery system and it has the following advantages :
l. There is no loss of coolant due to overflow on account of expansion.
2. As air does not enter the cooling system with this arrangement, corrosion of the cooling jackets and passages and deterioration of antifreeze is reduced appreciably.
3. Relatively smaller upper tank may be used with the radiator
Testing the Radiator Pressure Cap
Apply the proper cap testing adapter and radiator pressure cap to the tester head. Pump the tester until the pressure valve of the cap releases pressure.
The cap should hold pressure in its range as indicated on the tester gauge dial for one minute. If it doesn’t, replace it. Remove the cap from the tester and visually inspect the condition of the cap’s pressure valve and upper and
lower sealing gaskets. If the gaskets are hard, brittle, or deteriorated, the cap may leak when exposed to hot, pressurized coolant. It should be replaced with a new cap in the same pressure range.
The most common tool used to test a cooling system is the radiator pressure tester. A radiator pressure tester is really no more than a hand pump with a pressure gauge. The pressure tester is extremely handy for identifying the location of any leak within the cooling system. To use the tester, connect it to the radiator filler neck. Run the engine until it is warm, then pump the handle of the tester until its gauge reads the same pressure that is noted on the radiator cap. Watch the gauge. If the pressure drops, carefully check the hoses, radiator, heat Lore, and water pump for leaks. Often the leak will initially be obvious because coolant will spray out of the leak. If the pressure drops but there are no external leaks, suspect an internal leak.
Repairing Radiators
Most radiator leak repairs require the removal of the radiator from the vehicle. The coolant must be drained and all hoses and oil cooler lines disconnected. Bolts holding the radiator are then loosened and removed. The actual radiator repair procedures depend on the material of which it is made and the type of damage. Most radiator repairs are made by radiator specialty shops that employ technicians with knowledge of such work. If the
radiator is badly damaged, it should be replaced and the installation of a new one should be done as directed by the manufacturer. Many of today’s radiators have plastic tanks, which are not repaired. If these tanks leak, they are replaced.
PRESSURE CAP AND EXPANSION RESERVOIR
Radiator filler neck in modern use is covered with a pressure cap, which forms an air tight joint due to which the coolant is maintained at some pressure higher than the atmospheric. Due to this higher pressure the boiling point of coolant is raised. For approximately, 10 kpa increase in pressure, the boiling point is raised by 2.5°C. The following advantages thus result from the use of pressure cap ;
(i) The engine can operate at higher temperatures without boiling the coolant. As the rate of heat transfer from the cooling system to the atmosphere depends on the difference between coolant temperature and atmospheric temperature, this will result in additional heat transfer to the atmosphere. This means that for the same engine, a smaller radiator can be used.
(ii) The preparation of air-fuel mixture is improved at the higher operating temperatures.
(iii) with sealed cap, loss of coolant due to evaporation or surging is prevented, which makes the system particularly useful in deserts.
(iv) At high altitudes, the atmospheric pressure is low which causes the coolant to boil at a lower temperature. Thus under severe working conditions at high altitudes, e.g., during steep climb, the coolant in the radiator may boil if the system is open to atmosphere. with pressure cap, a higher pressure is maintained inside, irrespective of any change in the atmospheric pressure,
thus avoiding overhearing while driving at higher altitudes and thus maintaining the cooling efficiency of the system. A pressure cap. It contains a pressure valve and a vacuum valve. When due to severe working conditions, the coolant starts boiling and vaporises, the pressure in the system exceeds a certain predetermined value (50-100 kPa), the pressure blow-off valve opens
releasing the excess pressure to the atmosphere through the overflow pipe. on the -other hand if due to any reason (e.g. sudden cooling of the hot radiator), a vacuum is created inside, the vacuum valve operates to avoid collapse of the radiator. This valve is usually set to operate when the vacuum exceeds about 5 kPa. It is important to remember that a pressure cap should never be opened when the radiator is still hot, because on removing the cap, the pressure in the cooling system will suddenly drop, causing the boiling point of the coolant to be decreased all of a sudden. This causes the coolant to start boiling immediately, which may spill over and burn anyone standing nearby severely. Further, in case of loss of cap, the replacement cap must be of the same pressure rating as the original one. In some engines, instead of overflow pipe an expansion reservoir is provided. This is so connected with the radiator that it receives the excess coolant as the engine temperature increases, when the cooling water cools down, its volume decreases and the coolant in the reservoir returns to the radiator keeping the system full of coolant. The reservoir is usually made of translucent plastic so that it can indicate the level of the coolant anytime. such a system is also known as coolant recovery system and it has the following advantages :
l. There is no loss of coolant due to overflow on account of expansion.
2. As air does not enter the cooling system with this arrangement, corrosion of the cooling jackets and passages and deterioration of antifreeze is reduced appreciably.
3. Relatively smaller upper tank may be used with the radiator
Testing the Radiator Pressure Cap
Apply the proper cap testing adapter and radiator pressure cap to the tester head. Pump the tester until the pressure valve of the cap releases pressure.
The cap should hold pressure in its range as indicated on the tester gauge dial for one minute. If it doesn’t, replace it. Remove the cap from the tester and visually inspect the condition of the cap’s pressure valve and upper and
lower sealing gaskets. If the gaskets are hard, brittle, or deteriorated, the cap may leak when exposed to hot, pressurized coolant. It should be replaced with a new cap in the same pressure range.
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