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Diagnosing and servicing the various systems of an automobile require many different tools. Tools that are used to check the performance of a sys tem or component are commonly referred to as diagnostic tools. Tools designed for a particular purpose or system are referred to as special tools. This section looks at the common diagnostic and special tools required to service the different systems of a vehicle. ENGINE REPAIR TOOLSEngine repair and diagnostic tools are discussed in the following paragraphs. This discussion does not cover all of the tools you may need: Only the most commonly used are discussed. Details of when and how to use these tools are presented in here. ++++A screw-in compression gauge set. ++++ Proper engine rebuilding requires many different tools. ++++ A push-in compression gauge. ++++ A cylinder leakage tester. Compression Testers The operation of an engine depends on the compression of the air-fuel mixture within its cylinders. If the combustion chamber leaks, some of the mixture will escape while it’s being compressed, resulting in a loss of power and a waste of fuel. A compression gauge is used to check cylinder compression. The dial face on the gauge indicates pressure in both pounds per square inch (psi) and metric kilopascals (kPa). The range is usually 0 to 300 psi and 0 to 2,100 kPa. There are two basic types of compression gauges: the push-in gauge and the screw-in gauge. The push-in type has a short stem that is either straight or bent at a 45-degree angle. The stem ends in a tapered rubber tip that fits any size spark plug hole. After the spark plugs have been removed, the rubber tip is placed in the spark plug hole and held there while the engine is cranked through several compression cycles. Although simple to use, the push-in gauge may give inaccurate readings if it’s not held tightly in the hole. The screw-in gauge has a long, flexible hose that ends in a threaded adapter ( ++++3). This type of compression tester is often used because its flexible hose can reach into areas that are difficult to reach with a push-in-type tester. The threaded adapters are changeable and come in several thread sizes to fit 10 mm, 12 mm, 14 mm, and 18 mm diameter holes. The adapters screw into the spark plug holes in place of the spark plugs. Most compression gauges have a vent valve that holds the highest pressure reading on its meter. Opening the valve releases the pressure when the test is complete. Cylinder Leakage Tester If a compression test shows that any of the cylinders are leaking, a cylinder leakage test can be performed to measure the percentage of compression lost and help locate the source of leakage. A cylinder leakage tester applies compressed air to a cylinder, with the piston at the top of its bore, through the spark plug hole. A threaded adapter on the end of the air pressure hose screws into the spark plug hole. A pressure regulator in the tester controls the pressure applied to the cylinder. A gauge registers the percentage of air pressure lost from the cylinder when the compressed air is applied. The scale on the dial face reads 0% to 100%. A zero reading means there is no leakage in the cylinder. A reading of 100% indicates that the cylinder won’t hold any pressure. The location of the compression leak can be found by listening and feeling around various parts of the engine. Oil Pressure Gauge Checking the engine's oil pressure gives information about the condition of the oil pump, the pressure regulator, and the entire lubrication system. Lower-than normal oil pressures can be caused by excessive engine bearing clearances. Oil pressure is checked at the sending unit passage with an externally mounted mechanical oil pressure gauge. Various fittings are usually supplied with the oil pressure gauge to fit different openings in the lubrication system. Stethoscope A stethoscope is used to locate the source of engine and other noises. The stethoscope pickup is placed on the suspected component, and the stethoscope receptacles are placed in the technician's ears. Some sounds can be heard easily without using a listening device, but others are impossible to hear unless amplified, which is what a stethoscope does. It can also help you distinguish between normal and abnormal noise. The best results, however, are obtained with an electronic listening device. With this tool you can tune into the noise, which allows you to eliminate all other noises that might distract or mislead you. Transaxle Removal and Installation Equipment The engines of some FWD vehicles are removed by lifting them from the top. Others must be removed from the bottom and this requires special equipment. The required equipment varies with manufacturer and vehicle model; however, most accomplish the same thing. To remove the engine from under the vehicle, the vehicle must be raised. A crane and/or support fixture is used to hold the engine and transaxle assembly in place while the engine is being readied for removal. Then the engine is lowered onto an engine cradle. The cradle is similar to a floor jack and lowers the engine further so it can be rolled out from under the vehicle. Often a transverse-mounted engine is removed with the transaxle. The transaxle is separated from the engine after it has been removed. Ridge Reamer After many miles of use, a ridge is formed at the top of the engine's cylinders. Because the top piston ring stops traveling before it reaches the top of the cylinder, a ridge of unworn metal is left. This ridge must be removed to push the pistons out of the block without damaging them during engine rebuilding. This ridge is removed with a ridge reamer. The tool is adjusted for the bore, inserted into it, and rotated with a wrench until the ridge is removed. Ring Compressor A ring compressor is used to install a piston into a cylinder bore. The compressor wraps around the rings to make their outside diameter smaller than the inside diameter of the bore. With the compressor tool adjusted properly, the piston assembly can be easily pushed into the bore without damaging the bore or piston. There are three basic types of ring compressors. One style has an adjustable band with a ratchet mechanism to tighten it around the piston. Another style uses ratcheting pliers to tighten a steel band around the piston. The bands are available in a variety of sizes. The third type has a single band that is wrinkled. The band is tightened by moving a lever. Once the rings are totally compressed into the piston, a thumbscrew is tightened to hold the band in position. ++++ A stethoscope. ++++ A ridge reamer. ++++A piston ring compressor. ++++ A piston ring compressor with a steel band and ratcheting pliers. ++++ A piston ring expander. Ring Expander To prevent damage to the piston rings during removal and installation, a ring expander should be used. To install a piston ring, the ring must be made large enough to fit over the piston. The rings fit into the jaws of the expander and the handle of the tool is squeezed to expand the ring. Expand the rings only to the point where they can fit over the piston. Using an expander prevents the possibility of cracking or distorting the rings while they are being expanded. The tool also helps to prevent cut fingers caused by the edges of the rings. Ring Groove Cleaner Before installing piston rings onto a piston, the ring grooves should be cleaned. The carbon and other debris that may be present in the back of the groove won’t allow the rings to compress evenly and completely into the grooves. Piston ring grooves are best cleaned with a ring groove cleaner. This tool is adjustable to fit the width and depth of the groove. Make sure it’s properly adjusted before using it and make sure you don’t damage the piston while cleaning it. Dial Bore Indicator Cylinder bore taper and out-of-roundness can be measured with a micrometer and a telescoping gauge. However, most shops use a dial bore gauge. This gauge typically consists of a handle, guide blocks, a lock, an indicator contact, and an indicator. They also come with extensions that make them adaptable to various size bores. As the dial bore gauge is moved inside the bore, the indicator will show any change in the bore's diameter. Cylinder Hone and Deglazer The proper surface finish on a cylinder wall acts as a reservoir for oil to lubricate the piston rings and pre vent piston and ring scuffing. On most late-model engines, sleeves or inserts into the engine block pro vide this finish, and when damaged or worn, the sleeves are replaced. On other engines, the cylinder walls can be refurbished. Always refer to the manufacturer's recommendation before servicing cylinder walls. When the walls have minor problems, the bore can be honed. Honing sands the walls to remove imperfections. A cylinder hone usually consists of two or three stones. The hone rotates at a selected speed and is moved up and down the cylinder's bore. Honing oil flows over the stones and onto the cylinder wall to control the temperature and flush out any metallic and abrasive residue. The correct stones should be used to ensure that the finished walls have the correct surface finish. Honing stones are classified by grit size; typically, the lower the grit number, the coarser the stone. Cylinder honing machines are available in manual and automatic models. The major advantage of the automatic type is that it allows the technician to dial in the exact crosshatch angle needed. If the cylinder walls have surface conditions, taper, and out-of-roundness that are within acceptable limits, the walls only need to be deglazed. Combustion heat, engine oil, and piston movement combine to form a thin residue on the cylinder walls that is commonly called glaze. Most cylinder de-glazers or glaze breakers use an abrasive with about 220 or 280 grit. The glaze breaker is installed in a slow-moving electric drill or in a honing machine. Many de-glazers use round stones that extend on coiled wire from the center shaft. This type de-glazer may also be used to lightly hone the bore. Various sizes of resilient-based hone-type brushes are available for honing and deglazing. When cylinder surfaces are badly worn or excessively scored or tapered, a boring bar is used to cut the cylinders for oversize pistons or sleeves. A boring bar leaves a pattern similar to uneven screw threads. Therefore, the bore should be honed to the correct finish after it has been bored. Cam Bearing Driver Set The camshaft is supported by several friction-type bearings, or bushings. They are designed as one piece and are typically pressed into the camshaft bore in the cylinder head or block; however, some overhead camshaft (OHC) engines use split bearings to support the camshaft. Camshaft bearings are normally replaced during engine rebuilding. Cam bearings are normally press fit into the block or head using a bushing driver and hammer. V-Blocks The various shafts in an engine must be straight and not distorted. Visually it’s impossible to see any distortions unless the shaft is severely damaged. Warped or distorted shafts will cause many problems, including premature wear of the bearings they ride on. The best way to check a shaft is to place the ends of the shaft onto V-blocks. These blocks will support the shaft and allow you to rotate the shaft. Place the plunger of a dial indicator on the journals of the shaft and rotate the shaft. Any movement of the indicator's needle suggests a problem. Valve and Valve Seat Resurfacing Equipment Whenever the valves have been removed from the cylinder head, the valve heads and valve seats should be resurfaced. The most critical sealing surface in the valvetrain is between the face of the valve and its seat in the cylinder head. Leakage between these surfaces reduces the engine's compression and power and can lead to valve burning. To ensure proper seating of the valve, the seat area on the valve face and seat must be the correct width, at the correct location, and con centric with the guide. These conditions are accomplished by renewing the surface of the valve face and seat. Valve and valve seat grinding or re-facing is done by machining with a grinding stone or metal cutters to achieve a fresh, smooth surface on the valve faces and stem tips. Valve faces suffer from burning, pit ting, and wear caused by opening and closing mil lions of times during the life of an engine. Valve stem tips wear because of friction from the rocker arms or actuators. Valve Guide Repair Tools The amount of valve guide wear can be measured with a ball gauge and micrometer. If wear or taper is excessive, the guide must be machined or replaced. If the original guide can be removed and a new one inserted, press out the old valve guide with a properly sized driver. Then install a new guide with a press and the same driver. Some technicians knurl the old guide to restore the inside diameter dimension (ID) of a worn valve guide. Knurling raises the surface on the inside of the guide by plowing tiny furrows through the surface. This effectively decreases the ID of the guide. A burnisher is used to flatten the ridges and produce a proper-sized hole to restore the correct guide-to-stem clearance. Reaming is often done to increase a guide's ID to accept an oversized valve stem or a guide insert. Some valve guide liners or inserts are not precut to length and the excess must be milled off before finishing. ++++A valve grinding machine. ++++A typical spring compressor for OHC valves. Remove rocker arm; Compress spring with special tool or prybar ++++ A C-clamp valve spring compressor. ++++A torque angle gauge attached to the drive lug of a torque wrench. Torque angle gauge; Torque wrench Valve Spring Compressor To remove the valves from a cylinder head, the valve spring assemblies must be removed. To do this, the valve spring must be compressed enough to remove the valve keepers, then the retainer. There are many types of valve spring compressors. Some are designed to allow valve spring removal while the cylinder head is still on the engine block. Other designs are only used when the cylinder head is removed. The prybar-type compressor is used while the cylinder head is still mounted to the block. With the cylinder's piston at TDC, shop air is fed into the cylinder to hold the valve up and prevent it falling into the cylinder. Some OHC engines require the use of a special spring compressor. Often these special tools can be used when the cylinder head is attached to the block and when it’s on a bench. They bolt to the cylinder head and have a threaded plunger that fits onto the retainer. As the plunger is tightened down on the retainer, the spring compresses. C-clamp-type spring compressors can only be used on cylinder heads after they have been removed. These are normally equipped with interchangeable jaws and can be pneumatically or manually operated. One end of the clamp is positioned on the valve head and the other on the valve's retainer. After the compressor is adjusted, it’s activated to squeeze down on the spring. Once the spring is compressed, the valve keepers can be removed. Then the tension of the compressor is slowly released and the valve retainer and spring can be removed. Valve Spring Tester Before valve springs are reused, they should be checked to make sure they are within specifications. This checking should include their freestanding height and squareness. If those two dimensions are good, the spring should be checked with a valve spring tester. A valve spring tester checks each valve's open and close pressure. Correct close pressure guarantees a tight seal. The open pressure overcomes valvetrain inertia and closes the valve when it should close. The tester's gauge reflects the pressure of the spring when it’s compressed to the installed or valve closed height. Read the pressure on the tester and compare this reading to specifications. Any pressure outside the pressure range given in the specifications indicates the spring should be replaced. Torque Angle Gauge Most manufacturers recommend the torque-angle method for tightening cylinder head bolts, which requires the use of a torque angle gauge. Typically two steps are involved: Tighten the bolt to the specified torque, and then tighten the bolt an additional amount. The latter is expressed in degrees. To accurately measure the number of degrees added to the bolt, a torque angle gauge is attached to the wrench. The additional tightening will stretch the bolt and produce a very reliable clamp load that is much higher than can be achieved just by torquing. Oil Priming Tool Prior to starting a freshly rebuilt engine, the oil pump must be primed. There are several ways to pre-lubricate, or prime, an engine. One method is to drive the oil pump with an electric drill. With some engines, it’s possible to make a drive that can be chucked in an electric drill motor to engage the drive on the oil pump. Insert the fabricated oil pump drive extension into the oil pump through the distributor drive hole. To control oil splash, loosely set the valve cover(s) on the engine. After running the oil pump for several minutes, remove the valve cover and see whether there is any oil flow to the rocker arms. If oil reached the cylinder head, the engine's lubrication system is full of oil and is operating properly. If no oil reached the cylinder head, there is a problem either with the pump, with the alignment of an oil hole in a bearing, or perhaps with a plugged gallery. Using a pre-lubricator, which consists of an oil reservoir attached to a continuous air supply, is the best method of pre-lubricating an engine without running it. When the reservoir is attached to the engine and the air pressure is turned on, the pre lubricator will supply the engine's lubrication system with oil under pressure. ++++An engine pre-luber kit. SPX Service Solutions ++++Cooling system pressure tester. ++++ A refractometer checks the condition of the engine's coolant. ++++A coolant recycling machine that drains, back flushes, and fills the cooling system. ++++A simple 9-volt memory saver. Cooling System Pressure Tester A cooling system pressure tester contains a hand pump and a pressure gauge. A hose is connected from the hand pump to a special adapter that fits on the radiator filler neck. This tester is used to pressurize the cooling system and check for cool ant leaks. Additional adapters are available to connect the tester to the radiator cap. With the tester connected to the radiator cap, the pressure relief action of the cap may be checked. Coolant Hydrometer A coolant hydrometer is used to check the amount of antifreeze in the coolant. This tester contains a pickup hose, a coolant reservoir, and a squeeze bulb. The pickup hose is placed in the radiator coolant. When the squeeze bulb is squeezed and released, coolant is drawn into the reservoir. As coolant enters the reservoir, a float moves upward with the coolant level. A pointer on the float indicates the freezing point of the coolant on a scale located on the reservoir housing. Refractory Testers For many shops, the preferred way to check coolant is with a refractometer. This tester works on the principle that light bends as it passes through a liquid. A sample of the coolant is placed in the tester. As light passes through the sample of coolant, it bends and shines on a scale in the tester. A reading is taken at the point on the scale where there a separation of light and dark. Most refractory coolant testers can also check the electrolyte in a battery. Measuring pH Acids produced by bacteria and other contaminants can reduce the effectiveness of cool ant. Some shops measure the pH of coolant to deter mine deterioration of the coolant. The pH is measured by placing test strips or a digital pH tester into the coolant. Coolant Recovery and Recycle System A coolant recovery and recycle machine ( ++++17) typically can drain, recycle, fill, flush, and pressure test a cooling system. Usually additives are mixed into the used coolant during recycling. These additives either bind to contaminants in the coolant so they can be easily removed, or they restore some of the chemical properties in the coolant. ++++Typical circuit tester, commonly called a testlight. Next: Electrical/Electronic System Tools Prev.: Automotive Shop/Garage Equipment + Hand/Power Tools Home Article Index top of page |
