Fiat 500C

Fiat 500C

The 2010 Fiat 500C debuting at the Geneva Motor Show has the same dimensions as the coupe version: 3.55 m x 1.65 m x 1.49 m. It is also powered by the same three engines available in the hardtop: a 1.3-liter 75 hp Multi-jet turbo-diesel, 1.2-liter 69 hp gad unit, or 1.4-liter 100 hp gas engine. The big difference is what Fiat calls, "a fully fledged window to the sky."

Starting from the saloon version, the introduction of the soft top does not change the winning characteristics of the model such as its four comfortable seats and boot capacity, but it does add new functions that heighten enjoyment. These include easier access to the boot even when the soft top is fully open, thanks to a clever system of parallelogram hinges.

Another strong point of the original cabriolet version is its exceptional climate and acoustic comfort. Thorough aerodynamic research means that the turbulence experienced with the roof open has been reduced to a minimum, allowing full enjoyment of the fresh air and the company of fellow passengers.

A highly original exercise in design, the soft top of the Fiat 500C stands out for its refined electrically operated linkage and engineering solutions of great quality and finish, such as the glass rear window and the built-in centrally positioned high mounted stop light. Available in three colours (ivory, red and black), this original soft top will be matched with several body colours, two of which have been conceived specifically for the new car in a brilliant Pearl Red and a special Warm Grey.

The interior of the Fiat 500C is equally exclusive, and boasts top quality materials. In particular, the new sporty seats are upholstered in a high-quality fabric which constitutes an important feature of the car for its feel and durability. The back and cushion of the rear seats are very enveloping and the side panels are upholstered in leather. As an optional extra, the interior of the Fiat 500C can be upholstered in black, beige or red Frau leather. The chrome trim and a dashboard that matches the exterior colour and is decorated by an exclusive 500C logo complete an elegant and functional interior that can comfortably accommodate four people.

The soft top is also easy to use: to open it, just press the button for at least half a second to trigger the movement that then continues automatically up to the spoiler (a midway point can of course be chosen by pressing the button again). Press the button again for at least half a second to fully open the roof. When using the remote control, the roof can be opened only as far as the spoiler. The same processes will close it; for safety reasons, the roof stops at around 25 cm from complete closure (just press the button again to complete the movement).

The Fiat 500C offers an wide range of excellent engines: two are petrol (a 1.2 litre, 69HP 8v and a 1.4 litre, 100 HP 16v). The third is the 1.3 litre, 75 HP 16v Mult-iJet turbo-diesel with DPF. Each one offers different qualities, but all are combined with a five or six speed manual gearbox. (A Dualogic sequential robotised gearbox is also available for the petrol engines, complete with steering wheel paddle shift on the 1.4 version.) All engines boast a generous, lively temperament, high performance and sophisticated technology. Among their common qualities are excellent reliability and respect for the environment: they all conform to Euro5 standard, and the 1.3-litre Multi-Jet diesel is fitted with a diesel particulate filter as standard.

The power-operated cloth-top will reported come in three colors – ivory, red and black – and a new spoiler, incorporated into the retractable roof, keeps the third brake light visible whether to the top is up or down. Both the 1.2- and 1.4-liter engines will carry over, along with the 1.3-liter Multi-jet equipped with Start-Stop technology. Expect sales to begin later this year in Europe, with U.S. distribution likely in 2010.

CAR WALLPAPER

COOLINIG SYSTEM SERVICING 6

Different types of coolant pumps


The present trend is to make coolant pumps smaller and lighter. Light alloys are increasingly being used for pump bodies while use of synthetic resins is on increase for impellers. The shaft- bearing design in which shaft and bearings are combined in one unit has resulted in more compact design.

Thermo-responsive Coolant Pump

M/s Thompson Products Inc. (U.S.A.) have devised a pump with which the circulation of coolant is directly controlled by means of metallic vanes on the impeller, instead of by the use of thermostat valve. Bimetallic elements are provided on the periphery of the impeller. These elements control the apertures on the periphery of the impeller. under low temperature conditions the elements close the apertures and there is no pumping action. However, as the coolant temperature increases the elements deflect to open the apertures and the pump discharges coolant into circulation.

Check the radiator cap. If your cap is rusted or the rubber seal is dried out, it should be replaced. A pressure tester should be used to be sure the cap is operating at the recommended pressure level.

COOLING SYSTEM TROUBLE SHOOTING

The common faults occurring in the cooling system are described below. Along with their possible causes and suitable remedies.

1. Overheating. This may be caused due to any one or more of the following reasons. However, it must be borne in mind that the overheating is caused not only due to defects in the cooling system. Rather the same may be caused by many factors completely different. i.e., pertaining to other systems also, e.g., too much retarded ignition timing, weak air-fuel mixture etc. Check for internal leaks. Pull the oil dipstick and check for evidence of coolant. It will show up as minute droplets or sludge and should be easy to spot. This could indicate a cracked head, block or blown head gasket.

(i) Accumulation of rust or scale in the coolant jackets and the radiator. Rust and scale are both bad thermal conductors and thus the rate of heat transfer is decreased. This may be remedied by use of suitable chemicals (e.g ordinary washing soda) and reverse flushing. Reverse flushing is done by circulating water under pressure in the direction opposite to the normal. This is done with the help of special air pressure gun which forces the water through. Flushing of the engine and the radiator is done separately. The effect of the chemical is to loosen the scale and the reverse flushing then washes it away. An important precaution is to use only warm water for flushing a warm engine. In some cases the reverse flushing may cause damage to the engine. So before resorting to this, the manufacturer's manual must be studied.

(ii) Defective hose or faulty connections may be another source of overheating. Defective hose may become a source of the hose material accumulating in the radiator passages or engine water jackets while the faulty connections will cause leaking of coolant thus reducing the capacity of the cooling system to extract heat. The remedy is to replace the defective hose and to tighten the various connections, so that there is no more any leakage.

(iii) Sometimes the engine block may also be cracked, causing loss of coolant. This can be tested by plugging coolant inlet and outlet and pumping in the water under pressure. If the block is found cracked, the same may be suitably repaired.

(iv) Defective coolant pump reduces the volume of the coolant to be circulated and thus may be the cause of overheating. There is no definite method to test the coolant pump. However, if the upper hose is opened out and hand is placed over the water jacket outlet while the engine is running, then the feeling of some pressure (which one knows by experience) by the hand indicates that coolant pump is functioning normally. If it is not functioning properly, open it out and look for the defects, which may be
corrected.

Check the thermostat: Remove the radiator cap and start the engine. Insert a suitable thermometer into the radiator neck. When the coolant level drops in the radiator, the thermostat has opened and is allowing circulation. Record the temperature on the thermometer and compare to the thermostat specifications. It should be no more than a few degrees either way of the actual thermostat setting. If you are not in the correct range, the thermostat will have to be replaced. Be sure to install a new gasket and inspect the thermostat seating area for corrosion and pitting.
(v) A defective thermostat that may be sticking in the closed position will not allow the coolant to go to the radiator and be cooled there. As a result the engine will be overheated. The thermostat valve may be tested by taking it out and placing it in a hot water bath in which the thermometer is also placed. If the valve opens and closes at the same temperatures as specified in the manufacturer’s manual, it is alright; otherwise it is defective. The remedy in this case is to replace it.

(vi) Fan belt which is slipping may be another source of engine overheating. The slipping may be either due to the belt being loose or by the oiling of the belt or any of the pulleys. A loose belt may be tested by pressing it at the centre with hand. If the belt sags by more than 10- 15 mm with a force of 30-40 N, it is definitely loose and needs tightening, which is done by shifting the generator and retightening its belts. In MM-540 DP jeep the belt is tightened by screwing to bring index (3) in front of face (a) of flange marking. The oiled belt or pulleys should be cleaned with a piece of cloth. If the belt is otherwise defective, it should be replaced atonce.

(vii) The air passages in the radiator may be blocked. These may be opened up by blowing air under pressure from the fan side of the radiator. The fins of the radiator may also be damaged so as to obstruct the flow of air. The same may be corrected with pliers or screw driver.

(viii) Loss of coolant by evaporation may also be a cause of overheating, which may be corrected by filling the radiator to the correct level.

(ix) Radiator fan thermostat switch, if provided, may be defective. This can be tested by immersing the switch in hot water and testing its continuity If the switch conducts when the h6t water temperature rises to 86-90°C and it does not when the hot water temperature falls down to 81-85°C, it is in good condition. If found defective, the switch should be replaced.
2. Slow warm up (or overcooling). When the engine takes unduly more time to warm, defect may be also due to the thermostat valve being stuck open. It may be removed and tested. If found defective, the same has to be replaced.

3. Noisy coolant pump. If the coolant pump is making too much noise, the reason may be either defective seal or defective bearing. The only remedy is the replacement of the faulty components.

COOLINIG SYSTEM SERVICING 5

The following methods are currently being employed for this:

l. The fan blades are of variable pitch type, which is controlled by the engine speed itself. As the engine speed increases, the pitch decreases, thus reducing the air flow. Alternatively, the blade pitch is controlled directly by the cooling water temperature, which has been found to be more efficient design.

2. The fan is not directly driven by the belt from the crankshaft, but is driven through a fluid coupling. One rotor of the coupling is driven by the engine, while to the other one is attached the fan. The spacing between the rotors is controlled by the temperature of the cooling system, which changes the slip of the coupling thus changing the fan speed according to the
requirements.

3. The fan is driven by means of a separate electric motor which is supplied with power directly from the electric circuit of the engine. This system has been used on Maruti cars. A thermostat switch is placed at an appropriate place in the cooling system and depending upon the cooling
system temperature it operates to switch on or off the fan motor. It has been found that under ordinary conditions, only about 5 percent of the time the fan motor remains in ‘on’ position, while 95 per cent of the time it is ‘off.’ The saving of engine power thus achieved may, therefore, be well imagined.

Check the cooling fan. If the vehicle is equipped with a centrifugal thermo-static type fan clutch, it is important to spot problems before they occur. Check for wear by moving the fan blade back and forth. Over 1/4" of play in either direction could point towards excessive bearing wear. You should also turn the fan by hand. If it free-wheels or there is a rough grating feel as the fan turns, this could mean excessive fluid loss or bearing wear respectively. If any of these conditions exist or there is evidence of fluid leakage, the fan clutch should be replaced. If the vehicle is equipped with an electric cooling fan, a quick performance check can be made by turning on the A/C and checking to make sure it operates without excess vibration or noise. Also check all electrical connections for signs of corrosion, or physical damage. With the engine hot, check to see if the fan is coming on at the correct temperature and operating properly.

Checking Fans and Fan Clutches

Fan operation can be checked by spinning the fan by hand. A noticeable wobble or any-blade that is not in the same plane as the rest indicates that replacement is in order. The fan can also be checked by removing it and laying it on a flat surface. If it is straight, all the blades should touch the surface. Never attempt to straighten a damaged cooling fan. Bending it back into shape might seem easier (and cheaper) than replacing it, but doing so is risky. Whenever metal is bent, it is weakened Fan clutches use a fluid-filled chamber (usually silicone) to turn the fan. Obviously, loss of the drive fluid will render the fan useless. One of the simplest checks is to visually inspect the fan clutch for signs of fluid loss. Oily streaks radiating outward from the hub shaft mean fluid has leaked out past the bearing seal.
Most fan clutches offer a slight amount of resistance if turned by hand when the engine is cold. They offer drag when the engine is hot. If the fan freewheels easily hot or cold, replace the clutch. Another check that should be made is to push the tip of a fan blade in and out. Any visible looseness in the shaft bearing means the fan clutch should be replaced. Fan blades are balanced at the time of manufacture but can be bent if handled carelessly. Likewise, fan clutches are machined very accurately to run true. However, rough handling at the time of pump replacement causes nicks and dents on the mounting faces. This can cause the fan blade to be installed crookedly. Serious trouble might follow soon after the car is back in service. There-
fore, technicians should be cautioned to handle fan clutches and blades with care and to file away any nicks, burrs, or dents someone else might have caused. Obviously, if any fins have been broken off the fan clutch, it
must be replaced.


Checking Belts

If a belt breaks, at best the fan stops spinning and the coolant does not cool down efficiently. At worst, the water pump stops, the coolant does not circulate, and, eventually, the engine overheats. Belts, like hoses, are made of elastic rubber compounds. Although they are extremely sturdy, they are primarily designed for transmitting power. Even the best belts last only an average of four years. Advise the customer to replace all belts every four years, regardless of how they look. Fortunately, belt problems are easily discovered either by visual inspection for cracks, splits, glazing, or oil soak-age, or by the screech of slippage. In servicing a multi-belt setup, it is very important to replace all of the belts when one belt is bad. The mounting brackets on generators, power-steering pumps, and air compressors are designed to be adjustable so proper tension can be maintained on these belts. Some of these brackets have a hole or slot to allow the use of a pry bar or wrench when adjusting. Some automobiles require the fan, fan pulley, and other accessory drive belts to be removed to gain access to belts needing replacement. Always use the exact replacement size of belt. The size of a new belt is typically given, along with the part number, on the belt container. After replacing a belt, make sure it is adjusted properly. Some engines have an adjusting bolt that can be tightened to bring the belt tension to specifications. On other engines, it may be necessary to use a pry bar to move an accessory enough to meet tension specs. Be careful not to damage the part you are prying against. The belt’s tension should be checked with a belt tension gauge. When installing a serpentine belt, make sure it is fed in and around the accessories properly. Service manuals
show the proper belt routing. Also make sure the belt tensioner is working properly. After any drive belt has been installed with the correct tension, tighten any bolts or nuts that were loosened to move the belt. Misalignment of the V-pulleys reduces the belt’s service life and brings about rapid V-pulley wear. Undesirable side or end thrust loads can also be imposed on pulley or pump shaft bearings. It is important to check alignment by using a straightedge. Pulleys should be in alignment within 1/16 inch (1.59 mm) per foot of the distance across the face of the pulleys.

FLUSHING COOLING SYSTEM
Rust and scale will inevitably form in any cooling system. When they do, there are a few vulnerable places they can attack. One happens to be the main seal in the water pump, which keeps coolant away from the bearing and its lubricant. If grit is allowed to erode the seal, the bearing will be the next item to go. Coolant leaking from the water pump's vent hole is evidence of seal failure. Whenever coolant is changed, and especially before a water pump is replaced, a thorough reverse flushing or back flushing should be performed. Before this flushing is done, chemical cleaners can be added to the cooling system to help dissolve rust and scale deposits. Reverse flushing is the procedure of forcing clean liquid backwards through the cooling system. This carries away rust, scale, corrosion, and other contaminants. A flushing gun that operates on compressed air is used to force clean water and air through the system. This method of flushing the system is not recommended on systems that use plastic and aluminum radiators. Check the service manual for the proper way of cleaning out the cooling system on vehicles with those kinds of radiators.

Refilling and Bleeding
After the cooling system has been cleaned, refill the system with new coolant mixed to the recommend-ed strength. Be sure all the flushing water is out of the radiator and evacuated from the engine block before refilling.
The cooling system must be bled to ensure there are no air pockets in the coolant. Air in the system can reduce cooling ability and lead to water pump and other component damage. Each vehicle has its own specific bleeding procedure. In-many cases, the system are filled and the radiator cap is left off. The engine is then run until the thermostat opens and the coolant circulates. Tapped air bubbles escape through the opened radiator. Other bleeding procedures are more involved. They may require the connection of special bleeder hoses to air bleed valves located on the radiator or other components. Air is bled through the valves as the system is filled. Always follow the bleeding steps outlined in the vehicle’s service manual.

COOLANT PUMP

A coolant pump is a necessity for the forced circulation type of engine cooling system. The pump is mounted at the front end of the engine and is driven from the crankshaft by means of a V- belt. Centrifugal type pump is the one which is used for this purpose (5.14). The coolant from the radiator enters the pump at the centre where inlet is located. The flow of the coolant
depends upon the pump speed which is proportional to engine speed, This is desirable since at higher engine speeds more heat is developed which requires more cooling. The scroll is connected to the front of the engine to direct the coolant into the block. For V-engine the coolant pump has two outlets, one for each bank of cylinders.
components of a coolant pump.
The main parts of the pump are a casing
(l) and a shaft-mounted impeller
(2) having a number of vanes. The impeller shaft is mounted on bearing
(3) while the seal
(4) serves to prevent the leakage of coolant around the shaft.

When the impeller rotates, the coolant between the vanes is thrown outward due to the centrifugal force, thus forcing the cooled coolant at the periphery, with a force depending upon the speed of rotation of the pump spindle, which itself is proportional to the engine speed .This water leaving the periphery of the impeller tangentially and having maximum kinetic energy then enters the in volute or the scroll, which is a smoothly curved passage cast in the casing, whose cross-sectional area gradually increases towards the outlet port. Thus the enlarging scroll converts the kinetic energy of coolant to pressure energy. In this way a coolant pressure is created at the pump outlet that forces the coolant through the cooling system.

COOLINIG SYSTEM SERVICING 4

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.

COOLINIG SYSTEM SERVICING 3

THERMOSTAT





It is already discussed in Article I that only optimum cooling of the engine is desirable and overcooling results in deterioration of engine efficiency. To keep a rigid control over the cooling, therefore, a thermostat is used, which automatically keeps the cooling water temperature at a predetermined value. Moreover, it also helps the engine to reach the operating temperature as soon as possible after starting as the engines are designed to operate most efficiently over a small temperature range of 80°to 100°c.
Two types of thermostats are used in automobiles:
l. Bellows or aneroid type.
2. Wax or hydrostatic type.

Bellows type thermostat

It consists of metallic bellows particularly filled with some volatile liquid like acetone, alcohol or ether which boils between 70-85°c. A valve is attached to one end of the bellows, while to the other end is attached a frame which fits into the cooling passage. The thermostat is fitted in the coolant hose pipe at the engine outlet. When the engine after start is warming up, it is desired that the cooling system should not operate so that the engine warms up early. During this period, the thermostat valve remains closed, because the liquid inside as yet has not changed its state and, therefore, does not exert any pressure on the valve. As the thermostat valve is closed with the coolant pump running, to avoid excessive pressure build-up, a part of the
held-up coolant is made to circulate back through a by-pass to the pump inlet. But as the coolant temperature reaches a predetermined value, (about 80°C) the liquid inside the thermostat is converted into vapour which exerts a pressure on the valve, which begins to open, so that the water circulation through the radiator starts. The valve then opens gradually further as the water temperature rises, until it is fully open at about 90-95°C. Thus the thermostat controls the flow of water through the radiator according to the engine cooling requirements. In this type of the thermostat, the valve movement depends upon the difference between the vapour pressure in the bellows at any given temperature and the cooling system pressure.

Wax Thermostat

A wax-element thermostat manufactured by the Dole valve Co., Illinois, U.S.A. As the coolant is heated, it transmits its heat to the copper-loaded wax having high coefficient of volumetric thermal expansion (0.28% per °C) which expands so that the rubber plug contracts against the plunger and exerts a force on it upwards so that it moves vertically. This movement of the plunger opens a valve in the thermostat (not shown) to allow coolant to flow through the radiator. This type of thermostat, in contrast to the bellows type, is not sensitive to the pressure variations, as discussed above. Thus it is more reliable to operate within the specified temperature range, due to which reason, it is being increasingly used.


Testing the Thermostat
There are several ways to test the opening temperature of a thermostat. One method does not require that the thermostat be removed from the engine. Remove the radiator pressure cap from a cool radiator and insert a thermometer into the coolant. Start the engine and let it warm up. Watch the thermometer and the surface of the coolant. When the coolant begins to flow, this indicates the thermostat has started to open. The reading on the thermometer indicates the opening temperature of the thermostat. If the engine is cold and coolant circulates, this indicates the thermostat is stuck open and must be replaced. The other way to test a thermostat is to remove it. Suspend the thermostat completely submerged in a small container of water so it does not touch the bottom. Place a thermometer in the water so it does not touch the container and only measures water temperature. Heat the water. When the thermostat valve barely begins to open, read the thermometer. This is the opening temperature of this particular thermostat. If the valve stays open after the thermostat is removed from the water, the thermostat is defective and must be replaced. Several types of commercial testers are available. When using such a tester be sure to follow the manufacturer’s instructions. Markings on the thermostat normally indicate which end should face toward the radiator. Regardless of the markings, the sensored end must always be installed toward the engine. When replacing the thermostat, also replace the gasket that seals the thermostat in place and is positioned between the water outlet casting and the engine block. Generally, these gaskets are made of a composition fiber material and are die-cut to match the thermostat opening and mounting bolt configuration of the water outlet. Thermostat gaskets generally come with or without an adhesive backing. The adhesive backing of gaskets holds the thermostat securely centered in the mounting flange, leaving both hands of the technician free to align and bolt the thermostat securely in place.

Two-stage thermostat

The construction of a two stage thermostat is similar to ordinary single stage thermostats described above, except that in this there is an additional subvalve, which starts opening at lower temperature (say 79°C), thereby allowing limited circulation of the coolant during warm-up period, thus preventing peak temperature hot spots. The main valve starts opening at some higher temperature, say 88°C and both valves are fully open at 100°C. Both the valves are fully closed below 79°C, providing quicker warm-up of the engine. Thus a two-stage thermostat provides more precise control of engine temperature by reducing peak temperature in critical areas.

Checking and Replacing Hoses
Carefully check all cooling hoses for leakage, swelling and chafing. Also change any hose that feels mushy or extremely brittle when squeezed firmly. Be especially watchful for signs of splits when hoses are squeezed. These splits have a habit of bursting wide open under pressure. Also look for rust stains around the clamps. Rust stains indicate the hose is leaking, possibly because the clamp has eaten into the hose. Loosen the clamp, slide it back, and check for cuts. Do not over look the small by-pass hose on some models. It is located between the water pump and engine block. Also, check the lower radiator hose very carefully. This hose contains a coiled wire lining to keep it from collapsing during operation. If the wire loses tension, the hose can partially collapse at high speed and restrict coolant flow. This results in a very elusive overheating problem. When replacing a hose, drain the coolant system below the level that is being worked on. Use a knife to cut off the old hose and loosen or cut the old clamp. Slide the old hose off the fitting. If the hose is stuck, do not pry it off. You could possibly damage the inlet/outlet nipple or the attachment between the end of the hose and the bead. Carefully cut the stuck hose off its fitting.

Clean off any remaining hose particles with a wire brush or emery cloth. The fitting should be clean when installing the new hose. Burrs or sharp edges could cut into the hose tube and lead to premature failure. Coat the surface with a sealing compound. Place the new clamps on each end of the hose before positioning the hose. Do not reuse old spring-type clamps, even if they look good. Slide the clamps to about ¼ inch (6.35 mm) from the end of the hose after it is properly positioned on the fitting. Tighten the clamp securely. Do not over tighten.

COOLINIG SYSTEM SERVICING 2

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.

COOLINIG SYSTEM SERVICING 1

Components of water cooling system


RADIATOR

The function of the radiator is to ensure close contact of the hot coolant coming out of the engine with outside air, so as to ensure high rates of heat transfer from the coolant to air. A radiator consists of an upper (or header) tank, core and the lower (or collector) tank. Besides, an overflow pipe in the header tank and drain pipe in the lower tank are provided. Hot coolant from the engine enters the radiator at the top and is cooled by the cross-flow of air, while flowing down the radiator. The coolant collects in the collector tank from where it is pumped to the engine for cooling. There are two basic types of radiator cores, viz., tubular type and cellular type. In the former, it is the coolant that flows through tubes and air passes around them, while in the cellular type the air passes through the tubes and coolant flows in the spaces in between them. Out of these, tubular type cores are the most commonly used which are further classified depending upon the shape of the fins around the tubes, which are meant to increase the area for heat transfer from coolant to the cooling air. Both the core tubes as well as the fins are made from thinnest possible material. Tubes are made from 0.1 mm to 0.3 mm sheet, whereas fins are made from about 0.1 mm thick material. The materials used for radiators should be resistant to corrosion, possess higher thermal conductivity and form easily, apart from having adequate
strength. Copper and yellow brass are the widely used materials for. radiators. Aluminium is also used from weight and cost considerations. Some late model radiators have plastic tanks with aluminium cores. The size of the radiator must be adequate to remove the heat which is approximately equal to the heat, energy utilized producing power in the engine. Alternatively, the radiator size is matched to the displacement volume of the engine. The air conditioned vehicle would require a large radiator due to extra heat load on account of the compressor. Besides, it is also ensured that maximum cooling is attained with minimum air resistance. Thus frontal area of the radiator is kept minimum, which may be achieved by making the core thicker and accommodating more core material into the same volume without increasing the air resistance. For heavy duty applications, radiators shutters are also sometimes used.
These are automatically controlled by means of the compressed air taken from the brake system. Shutter control mechanism is installed with the upper hose of the cooling system. Depending upon the coolant temperature coming from the engine, which itself depends upon the engine temperature, the shutter control mechanism causes the shutter to open or close. Thus, for example, the shutter remains closed during starting and it gradually opens up as the engine attains its working temperature, thus allowing the fresh air to come into contact with the radiator.

COOLINIG SYSTEM SERVICING
The cooling system must operate, be inspected, and be serviced as a system. Replacing one damaged part while leaving others dirty or clogged will not increase system efficiency. Service the entire system to ensure good results. Service involves both a visual inspection of the parts and connections and pressure testing. Pressure testing is used to detect internal or external leaks. The following is a list of places to check for a suspected leak in the cooling system. Although this is not a complete list, it does present the most common areas where a leak can occur.

External Leakage:
Radiator
Loose hose clamp
Hose
Faulty radiator cap
Dented radiator hose connector for the inlet or outlet hose
Heater connection
Water pump, through weep hole
Cracked or porous water pump housing & Heater core
Loose core hole plug in cylinder block
Cracked thermostat housing
Water temperature sending unit
Cylinder head bolts loose or tightened unevenly
Warped or cracked cylinder head
Heater control valve
Cracked cylinder block
Damaged gasket or dry gasket if engine has been stored
Coolant reservoir or hose
Internal Leakage:
Faulty head gasket
Cracked head
Cracked block
Transmission fluid cooler

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