Water pump Service
The majority of water pump failures are attributed to leaks of some sort. When the pump seat fails, coolant will begin to seep out of the weep hole in the casting. This is an early indicator of trouble. The seals may simply wear out due to abrasives in the cooling system, or some types of seals crack due to thermal shock such as adding cold water to an overheated engine. This could also cause other internal parts to fail. Other failures can be attributed to bearing and shaft problems and an occasional cracked casting. Water pump bearing or seal failure can be caused by surprisingly small out-of-balance conditions that are difficult to spot. Look for the following:
A bent fan. A single bent blade will cause problems.
A piece of fan missing.
A cracked fan blade. Even a small crack will prevent proper flexing.
Fan mounting surfaces that are not clean or flush.
A worn fan clutch.
To check a water pump, start the engine and listen for a bad bearing, using a mechanic’s stethoscope or rubber tubing. Place the stethoscope or hose on the bearing or pump shaft. If a louder than normal noise is heard, the bearing is defective. There is another test that can be performed on vehicles with an engine-driven fan. With the engine off and the fan belt and shroud removed, grasp the fan and attempt to move it in and out and up and down. More than 1/16 inch (1.58 mm) of movement indicates worn bearings that require water pump replacement. To determine whether the water pump is allowing for good circulation, warm up the engine and run it at idle in speed. Squeeze the upper hose connection with one hand and accelerate the engine with the other hand. If a surge on the hose is felt, the pump is working. Any air being sucked into the cooling system is certain to have a detrimental effect. It cuts down pumping efficiency and causes both rusting and wear at a rate approximately three times above normal. To test for aeration, have the engine fully warmed up, all hose connections tight, and the coolant level up to normal. Attach one end of a small hose to the radiator overflow pipe and put the other end into a jar of water. Run the engine at a fast idle. If a steady stream of bubbles appears in the jar of water, air is getting into the cooling system. Check first for a cylinder gasket leak by running a compression test. If two adjacent cylinders test low the gasket is bad. Otherwise, there is an air leak somewhere else in the cooling system.
REPLACING THE WATER PUMP
When replacing a water pump, it is necessary to drain the cooling system.
Any components-belts, fan, fan shroud, shaft spacers, or viscous drive clutch-should be removed to make the pump accessible. Some pumps are attached to the cylinder block as shown in. Loosen and remove the bolts in a crisscross pattern from the center outward. Insert a rag into the block opening and scrape off any remains of the old gasket.
When replacing a water pump, always follow the procedures recommended by the manufacturer. Most often a coating of good waterproof sealer should be applied to a new gasket before it is placed into position on the water pump. Coat the other side of the gasket with sealer, and position the pump against the engine block until it is properly seated. Install the mounting bolts and tighten them evenly in a staggered sequence to the torque specifications with a torque wrench. Careless tightening could cause the pump housing to crack. Check the pump to make sure it rotates freely.
The water pumps on many late-model OHC engines are driven by the engine’s timing belt. When replacing the water pump on these engines, always replace the timing belt. Make sure all pulleys and gears are aligned according to specifications when installing the belt.
FAN
when the vehicle is going at high speed with light load, the natural draft of air passing through the radiator may be sufficient for cooling of the engine, but when the vehicle is moving under heavy load and at a slow speed e.g. when driving uphill, the natural draft is certainly insufficient to produce the desired cooling. This explains why fan is a necessary part of the engine cooling system. It is mounted behind the radiator on the same shaft on which the water pump is mounted. It is driven by a v-belt from the crankshaft pulley. It may have four to seven blades, sometimes spaced unevenly to reduce noise. It is generally made of sheet metal, but these days moulded plastic materials e.g., nylon or polypropylene are also being used for making fans. Sometimes the fan is mounted inside a thin plastic or metal housing around its periphery. This housing is attached behind and against the radiator and is called/an shroud. It allows fan to pull more air past the radiator. For efficient and economical running, it is required that the fan must give adequate air flow at all the conditions of vehicle load and speed. More flow than the minimum necessary for effecting cooling at any particular time is simply uneconomical. Thus the commonly used method of running the fan at one constant speed ratio with the engine is not desirable. If, for example, the fan is designed to give adequate air flow at low vehicle speeds, say, when going uphill when the air flow due to vehicle speed is very small, obviously the air draught at high vehicle speeds will be much more than the desired, when the air flow due to vehicle speed itself is quite high. Thus a fan that is always running when the engine runs, will be unnecessarily consumingengine power which has been estimated as much as 5 per cent of the engine
B.P. and producing more noise. This is clearly wastage and must be avoided.
The majority of water pump failures are attributed to leaks of some sort. When the pump seat fails, coolant will begin to seep out of the weep hole in the casting. This is an early indicator of trouble. The seals may simply wear out due to abrasives in the cooling system, or some types of seals crack due to thermal shock such as adding cold water to an overheated engine. This could also cause other internal parts to fail. Other failures can be attributed to bearing and shaft problems and an occasional cracked casting. Water pump bearing or seal failure can be caused by surprisingly small out-of-balance conditions that are difficult to spot. Look for the following:
A bent fan. A single bent blade will cause problems.
A piece of fan missing.
A cracked fan blade. Even a small crack will prevent proper flexing.
Fan mounting surfaces that are not clean or flush.
A worn fan clutch.
To check a water pump, start the engine and listen for a bad bearing, using a mechanic’s stethoscope or rubber tubing. Place the stethoscope or hose on the bearing or pump shaft. If a louder than normal noise is heard, the bearing is defective. There is another test that can be performed on vehicles with an engine-driven fan. With the engine off and the fan belt and shroud removed, grasp the fan and attempt to move it in and out and up and down. More than 1/16 inch (1.58 mm) of movement indicates worn bearings that require water pump replacement. To determine whether the water pump is allowing for good circulation, warm up the engine and run it at idle in speed. Squeeze the upper hose connection with one hand and accelerate the engine with the other hand. If a surge on the hose is felt, the pump is working. Any air being sucked into the cooling system is certain to have a detrimental effect. It cuts down pumping efficiency and causes both rusting and wear at a rate approximately three times above normal. To test for aeration, have the engine fully warmed up, all hose connections tight, and the coolant level up to normal. Attach one end of a small hose to the radiator overflow pipe and put the other end into a jar of water. Run the engine at a fast idle. If a steady stream of bubbles appears in the jar of water, air is getting into the cooling system. Check first for a cylinder gasket leak by running a compression test. If two adjacent cylinders test low the gasket is bad. Otherwise, there is an air leak somewhere else in the cooling system.
REPLACING THE WATER PUMP
When replacing a water pump, it is necessary to drain the cooling system.
Any components-belts, fan, fan shroud, shaft spacers, or viscous drive clutch-should be removed to make the pump accessible. Some pumps are attached to the cylinder block as shown in. Loosen and remove the bolts in a crisscross pattern from the center outward. Insert a rag into the block opening and scrape off any remains of the old gasket.
When replacing a water pump, always follow the procedures recommended by the manufacturer. Most often a coating of good waterproof sealer should be applied to a new gasket before it is placed into position on the water pump. Coat the other side of the gasket with sealer, and position the pump against the engine block until it is properly seated. Install the mounting bolts and tighten them evenly in a staggered sequence to the torque specifications with a torque wrench. Careless tightening could cause the pump housing to crack. Check the pump to make sure it rotates freely.
The water pumps on many late-model OHC engines are driven by the engine’s timing belt. When replacing the water pump on these engines, always replace the timing belt. Make sure all pulleys and gears are aligned according to specifications when installing the belt.
FAN
when the vehicle is going at high speed with light load, the natural draft of air passing through the radiator may be sufficient for cooling of the engine, but when the vehicle is moving under heavy load and at a slow speed e.g. when driving uphill, the natural draft is certainly insufficient to produce the desired cooling. This explains why fan is a necessary part of the engine cooling system. It is mounted behind the radiator on the same shaft on which the water pump is mounted. It is driven by a v-belt from the crankshaft pulley. It may have four to seven blades, sometimes spaced unevenly to reduce noise. It is generally made of sheet metal, but these days moulded plastic materials e.g., nylon or polypropylene are also being used for making fans. Sometimes the fan is mounted inside a thin plastic or metal housing around its periphery. This housing is attached behind and against the radiator and is called/an shroud. It allows fan to pull more air past the radiator. For efficient and economical running, it is required that the fan must give adequate air flow at all the conditions of vehicle load and speed. More flow than the minimum necessary for effecting cooling at any particular time is simply uneconomical. Thus the commonly used method of running the fan at one constant speed ratio with the engine is not desirable. If, for example, the fan is designed to give adequate air flow at low vehicle speeds, say, when going uphill when the air flow due to vehicle speed is very small, obviously the air draught at high vehicle speeds will be much more than the desired, when the air flow due to vehicle speed itself is quite high. Thus a fan that is always running when the engine runs, will be unnecessarily consumingengine power which has been estimated as much as 5 per cent of the engine
B.P. and producing more noise. This is clearly wastage and must be avoided.
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