A1-Engine Repair
A. The valve stems are hardened and cannot be knurled.
Which of the following is NOT a method correcting excessive valve stem-to-guide clearance? A. Knurling the valve stem B. Knurling the guide C. Reaming for oversize D. Guide replacement
D. If an exhaust valve is not seating, air will leak from the combustion chamber by way of the valve out to the tailpipe and make an audible sound. Broken rings or a bad head gasket would have air leaking through the oil filler or cooling system.
A Compression test shows that one cylinder is too low. A leakage test on that cylinder shows that there is excessive leakage. During the test, air could be heard coming from the the tail pipe. Which of the following could be the cause A. Broken piston ring B. Bad head gasket C.Bad exhaust gasket D.An exhaust valve not seating
D. Answer A is wrong because not all ethylene glycol coolant is the same and different ethylene glycol based coolants come with different corrosion inhibitor packages. Color alone cannot be used to determine the type of coolant that is in the system or container. For optimum system protection, use the type of coolant specified by the vehicle manufacturer. Answer B is wrong because while a mix of 50/50 is usually the most effective mixture, some manufacturers may specify otherwise. Answer C is wrong because even if a vehicle does not have a bleeder valve, the system still must be bled to keep air from from becoming trapped in the system. Remove a hose from the highest point (usually at the heater core) and fill the system until coolant begins to come out of this point. Start the engine and as soon as the level in the radiator drops, top it off and install the cap. Fill the reservoir to the indicated level.
A Technician has just flushed a cooling system. Which of the following statements should he adhere to when refilling the system? A. Make sure the fresh antifreeze is the same color as that which was drained B. Use a 50/50 mix of water and antifreeze. C. Bleed air from the system only if the vehicle has a bleeder valve D. None of the above
D. Neither Tech A or B- Core plugs are usually exposed to coolant and can corrode from the inside. A core plug may look fine on the outside, but in reality be paper thing from corrosion, so to be safe, all core plugs should be replaced. Any studs should be removed on an as-required basis. If the studs interfere with allowing the head to be properly setup for a machining operation, or if the studs could be easily damaged during cleaning, then they should be removed. However, some studs may be difficult to remove without breaking them and attempts to remove them may cause more problems than leaving them in place.
A cylinder head is being disassembled. Tech A says that if a core plug appears to be OK, then it should be left in place. Tech B says that all studs should be removed. Who is right? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
D. If the shop was located at sea level, any of the other answers might be indicated by this vacuum reading. But remember, atmospheric pressure changes with elevation and vacuum readings must be adjusted accordingly. As as approximation for every 1000ft above sea level, remove one inch of vacuum. If we correct for elevation, we can see that this engine would produce 19in Hg of vacuum at idle at sea level, which is within the parameters for normal engine operation.
A manifold vacuum test is performed on an engine in a shop that is located approximately 4000ft (1.2km) above sea level. With the engine at normal operating temperature, the gauge reads a steady 15in. hg at idle. Which of the following is indicated by this vacuum reading? A. Late ignition timing B. Low compression C. Vacuum leak D. Normal Operation
c. Both Technicians A and B. One rod bearing showing wear that is different than the rest could have an obstruction in the crankshaft oil passage that supplies the bearing, or an out of round rod bore.
A single rod bearing shows excessive wear, but the rest show normal wear. Tech A says this could be due to an out of round connecting rod bore. Tech B says that this could be due to an obstruction in the crankshaft oil passage that supplies the bearing. Who is right? A. Tech A B. Tech B C. Tech A and B D. Neither Tech A or B
D. Tapping noises are most often caused by loose valve train clearance or worn components. However, a tapping sound that may sound like a valve train noise can actually be caused by an exhaust manifold/cylinder head juncture.
A tapping noise can be heard coming from the upper part of an engine running at idle. Which of the following could be the cause? A. Valve clearance out of adjustment B. Worn rocker arm shaft C. Loose exhaust manifold D. All of the above
A. Only Tech A is correct. A burned valve will not allow the cylinder to build compression, and the results from wet and dry compression tests will be the same. If piston rings (or worn cylinders) were at fault, compression readings from a wet tests would exceed dry test results. Resources: http://www.mhnetwork.com/news/properly-diagnose-your-customer-s-engine-problems/
A technician takes a compression reading on a 4- cylinder engine, and gets readings of 140, 135, 135 and 40 psi. Then he performs a wet compression test, and the readings are almost the same as those in the first test. Tech A says that a burned valve could cause these readings. Tech B says that a broken piston ring could cause these readings. Who is right? A. Tech A B. Tech B C. Both Tech A and Tech B D. Neither Tech A or Tech B
B. Gasket sealer must not be used on synthetic rubber gaskets. It acts like a lubricant, causing the gasket to slip and leak.
A timing cover is being installed using synthetic rubber gasket. Tech A says that a 1/8-in. (3.175mm) to 3/16-in. (4.762mm) wide base of sealer should be applied along the length of the cover flange and block surface. Tech B says the gasket must be installed against a perfectly clean and dry surface. Who is right? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
D. A leaking intake manifold gasket or worn piston rings would not cause a vacuum gauge needle to fluctuate. Worn valve guides would make the needle fluctuate at idle, but the needle would steady when engine speed increases. A weak or broken valve spring will cause a vacuum gauge to fluctuate or jump from low to high readings.
A vacuum gauge is connected is connected to the intake manifold of an engine and the engine is run at 2000 rpm. During the test, the pointer on the gauge fluctuates rapidly between readings of 10 and 22 inches of vacuum. These test results point to: A. A leaking intake manifold B. Worn piston rings C. Worn valve guides D. A weak or broken valve spring
B. Worn valve guides would cause the gauge needle to fluctuate rapidly at idle but steady as the engine speed increased. A leaking intake manifold gasket or late ignition timing would cause a steady low reading. A weak valve spring would cause the needle to fluctuate as engine speed increases Resources: https://www.motor.com/magazine-summary/mastering-the-basics-reading-a-vacuum-gauge/ https://dannysengineportal.com/how-to-do-a-vacuum-test/
A vacuum gauge is connected to the intake manifold of an engine running at idle. The pointer on the gauge fluctuates rapidly but steadies as the engine speed is increased. The test results indicate: A. A leaking intake manifold gasket B. Worn valve guides C. Late ignition timing D. A weak valve spring
B. Both excessive main bearing clearance and excessive crankshaft end-play could cause a deep knocking sound in an engine. However, since the noise diminishes when the clutch is disengaged, it is due to excessive crankshaft end-play. Excessive crankshaft end-play means there is excessive clearance between the crankshaft thrust flange and the thrust bearing surface. When the clutch pedal is depressed, the crankshaft is forced against the thrust bearing, reducing this clearance.
A vehicle with a manual transmission has a deep knocking sound coming from the engine. The knocking sound diminishes when the clutch pedal is depressed. Tech A says the cause of the sound is excessive main bearing clearance. Tech B says that the cause is excessive crankshaft end play. Who is right? A. Tech A B. Tech B C. Both Tech A and Tech B C. Neither Tech A or B
A. B is wrong because the leak down rate is the time it takes the plunger to move a certain distance, not the distance the plunger moves within a certain period of time.
After reassembling a hydraulic lifter, Tech A says that it should be tested with a leak down tester. Tech B says that the leak down rate is how far the lifter plunger moves within a set time period. Who is right? A. Tech A B. Tech B C. Both Tech A and Tech B D. Neither Tech A or Tech B
B. Magnafluxing is used to detect cracks, not repair them.
All of the following are methods of repairing a cracked block EXCEPT: A. Pinning B. Magnafluxing C. Gluing D. Welding
D. A properly operating fan clutch will change the speed of the fan according to the engine temperature. When the engine is cold, the fan clutch does not turn the fan very fast, even when engine speed increased. As the engine warms up, the fan clutch increases the speed of the fan. If the fan speed varies only according to engine speed, regardless of temperature, then the fan clutch is probably seized and ship be replaced.
All of the following are statements describing normal mechanical fan clutch operation EXCEPT: A. A fan clutch has viscous drage regardless of temperature. B. A fan clutch varies fan speed according to engine temperature. C. A fan clutch stops the fan from spinning withing two seconds after turning off a hot engine. D. A fan clutch varies fan speed according to engine speed.
C. Amperage that is too low may be caused by starter circuit resistance. All of the other answers are true statements regarding a starter current draw test.
All of the following are true statements regarding a starter current draw test EXCEPT: A. As a general rule, current draw on a V8 should be higher than on a 4-Cyl engine B. Battery voltage should remain above 9.6v during the battery test C. Higher than normal current draw readings can be caused by excessive resistance in the starter circuit D. Higher than normal current draw readings can be caused by engine mechanical problems
C. Caustic will damage aluminum
All of the following are ways to clean an aluminum engine except A. Cold solvent tank B. Carburetor cleaner C. Hot caustic tank D. Pyrolytic oven
B. A cracked valve cover gasket and worn rear main seal would allow oil t leak past their damaged surfaces. Worn piston rings would cause excessive crankcase pressure to push oil past seals and gaskets that are in good condition. A stuck open PCV would not cause excessive crankcase pressure, but would cause a vacuum leak and cause the engine to run rough at idle.
All of the following can cause an engine oil leak EXCEPT: A. Cracked valve cover gasket B. Stuck open PCV valve C. Worn rear main seal D. Worn piston rings
B. Worn pistons can cause noise and accelerate ring and bore wear, but would not cause low oil pressure. Diluted oil, excessive bearing clearance and clogged pump pickup can all cause low oil pressure.
All of the following can cause low oil pressure EXCEPT: A. Diluted engine oil B. Worn pistons C. Excessive bearing clearance D. Clogged oil pump pickup
C. Resurfacing the block deck will decrease the deck height ( the distance from the top of the pistons at TDC to the top of the block) and raise compression.
All of the following can result from resurfacing a cylinder block EXCEPT: A. Change in the camshaft timing on an overhead camshaft engine B. Change in alignment between the cylinder heads and intake manifold on a V8 engine C. Decreased Compression D. Change in the valvetrain geometry on a pushrod engine
D. A dirty air filter and restricted exhaust would inhibit air flow through the turbocharger and reduce performance. Worn turbocharger shaft bearings could cause the rotating assembly to bind or drag and reduce performance. A stuck open wastegate would reduce performance. However a stuck closed wastegate would cause overboost.
All of the following could case reduced performance from a turbocharged engine EXCEPT: A. Dirty air filter B. Restricted exhaust system C. Worn turbocharger bearings D. Stick Closed wastegate
D. A thermostat that is stuck open will not restrict the coolant flow. A clogged cooling system would restrict coolant flow and cause engine overheating. A defective fan clutch and broken fan shroud would both reduce air flow through the radiator and could cause engine overheating.
All of the following could cause an engine to overheat EXCEPT: A. Defective fan clutch B. Clogged cooling system C. Broken fan shroud D. Stuck open thermostat
B. Retarded ignition timing. Ignition timing that is too far advanced would cause pinging or detonation, but retarded ignition timing would not. Excessive cylinder head resurfacing would raise compression and could cause pinging or detonation. An inoperative EGR valve would let combustion chamber temperatures become too high and could cause pinging or detonation. Fuel with too low an octane rating will burn too quickly and can be ignited by hot spots in the combustion chamber.
All of the following could cause an engine to ping or detonate EXCEPT: A. A faulty EGR valve B. Retarded ignition timing C. Excessive machining of the cylinder head D. Using fuel with too low of an octane reading
B. Magnetic particle detection can only be used can be used on ferrous (iron and steel) parts.
All of the following methods can be used to find cracks in aluminum heads EXCEPT: A. Pressure Tests B. Magnetic Particle Detection C. Visual Inspection D. Dye Penetrate
C. During a load test, a battery should be loaded to one-half its CCA rating for 15 seconds.
All of the following statements about batteries are true EXCEPT: A. A fully charged battery should have a specific gravity of 1.260 B. If the open circuit voltage is less than 12.4 volts, charge the battery at a slow rate C. A battery is load tested to on-third of its CCA (Cold Cranking Amps) rating for 15 seconds D. At the end of a load test, battery voltage must be 9.6 volts or more
C. Rings are installed on the piston using a ring extender. they are installed in the cylinder using a ring compressor.
All of the following statements about piston rings are true EXCEPT: A. Ring end gap must be measured prior to installation. B. Rings must be installed facing the correct vertical direction C. Rings are installed on the piston using a ring compressor D. Ring end gaps must be staggered around the piston
A. When you eliminate the ignition or injection to a cylinder with a rod knock, the sound diminishes. Unlike a connecting rod bearing noise, piston slap does not quiet down and may in fact grow louder when you eliminate ignition or fuel injection to the cylinder.
An engine has a light metallic knocking noise during light engine loads. However, when the cylinder with the noise is disabled during a cylinder power balance test the sound diminishes. Tech A says that the noise is caused by excessive connecting rod bearing clearance. Tech B says that the noise is caused by excessive piston to wall clearance. Who is right? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
C. Adding 0.020 to 2.1032 is 2.1232, which is right in the middle of the standard specifications, so 0.020-in. undersized bearings should be used.
An engine is being rebuilt and the crankshaft connecting rod journals have been ground undersized. Specifications show that the original connecting rod journal size was 2.1228-in. 21236-in. If the journals now measure 2.1032-in., what size bearings should be used? A. 0.001-in. undersized B. 0.010-in. undersized C. 0.020-in. undersized D. 0.030-in. undersized
A. A bent crankshaft could cause more wear on both bearings, in the center of a block; straightening or replacing the crankshaft would be the correct repair. A warped block would cause wear on either the upper or the lower bearing, depending on how the block was warped.
An engines upper and lower center main bearings show more wear than the ones towards either end of the crankshaft. Tech A says this wear pattern could be due to a bent crankshaft and replacing it with one that is straight will fix the problem. Tech B says that the cylinder block main bearing bores are misaligned and the problem can be fixed by align boring or honing the block. Who is right?
C. Worn piston rings will usually make an engine smoke worse under acceleration. All of the other causes can allow oil to be drawn through the valve guides under the high intake vacuum that occurs during deceleration.
Blue-gray smoke comes from the exhaust of a vehicle during deceleration. of the following, which is the LEAST likely cause? A. Worn valve seals B. Broken valve seals C. Worn piston rings D. Clogged oil return passages
B. The height of the lobes on the camshaft. The distance the valves are opened is defined as valve lift. The time that the valves stay open is usually referred to as duration.
Camshaft lift is defined as: A. The distance the valves are open B. The height of the lobes on the camshaft C. The time the valves stay closed D. The time the valves stay open
D. All of the above. The crankshaft main and rod journals should be inspected and measured for diametier, out of round and taper wear.
Crankshaft journals should be measured for: A. Diameter B. Out of round C. Taper D. All of the above
D. All of the spark plugs should be removed so the engine cranks more easily
In order to perform a proper compression test, all of the following conditions should be met EXCEPT: A. The throttle blades should be held wide open B. The battery should be fully charged C. The engine should be at operating temp D. Only the spark plug for the cylinder to be tested should be removed
A. If not within specification, spring installed height can be corrected by installing shim(s) between the valve spring and cylinder head. If spring free height, squareness or pressure is not within specification, the spring must be replaced.
Of the following spring measurements, which would NOT require spring replacement if the measurement is not withing specification? A. Installed Height B. Pressure C. Free height D. Squareness
D. A new timing chain should always be installed on new sprockets. Unless they are damaged, it is usually not necessary to replace the sprockets when replacing a timing belt.
Tech A is rebuilding an engine with a timing chain. Tech B is rebuilding an engine with a timing belt. Tech A says that the timing chain is stretched and must be replaced, however the timing sprockets appear to be in good shape so they can be reused. Tech B says he is replacing the timing belt and that requires him to also replace the timing sprockets. Who is correct? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
A. A tight belt will cause wear to the upper front main bearing. When an oil supply problem has resulted in a knock, the bearings furthest from the oil pump suffer first.
Tech A says if only the upper front main bearing is worn, a belt adjusted too tight is indicated. Tech B says when an engine with a knock is disassembled, the connecting rod bearing(s) closest to the oil pump will show the most wear. Who is right? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
C. Both technicians are correct
Tech A says if the camshaft bores are more than 0.0015-in. (0.0381mm) out of round, they should be align bored or align honed. Tech B says that the block needs to be align bored or honed if bore alignment is not within 0.0015-in. (0.0381mm). Who is right? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
C. Both Techs. A clearance ramp cushions the take up of clearance between the rocker arm or cam follower. Excessive lash causes the cam lobe to be contacted after the clearance ramp has passed.
Tech A says that a burned valve could be the result of too little valve lash. Tech B says excessive valve lash could cause very fast camshaft wear. Who is right?
B. When a cylinder is bored, 0.0025-0.003-in. (0.064mm-0.076mm) cylinder wall material is left for finish honing to final size. This is necessary to completely remove the rough finish left by the boring tool. Following normal honing, some manufacturers recommend a plateau finish in the bore, Plateau honing levels of the peaks left in the bore surface from honing. A a final polishing step it forms flat plateau areas between the grooves or valleys of the cross hatch. A plateau surface retains oil and allows faster ring seating while reducing ring and cylinder wear.
Tech A says that a cylinder should be bored to withing 0.001-in. (00.025mm) of final size. Tech B says that a plateau finish on the cylinder block will help seat the piston rings. Who is right? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
A. A sleeve can be used to repair a damaged or cracked cylinder bore
Tech A says that a deep gouge in a cylinder bore can be repaired by installing a sleeve. Tech B says a crack in a cylinder bore requires that the block be replaced. Who is right. A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
C. Both Technicians A and B. The outer ring on a defective harmonic balancer can slip, causing inaccurate ignition timing readings. A broken crankshaft can also result from an incorrect or defective balancer.
Tech A says that a defective harmonic balancer can cause inaccurate ignition timing readings. Tech B says that a defective harmonic balancer can cause a broken crankshaft. Who is right? A. Tech A B. Tech B C. Both Tech A and Tech B D. Neither Tech A or Tech B
C. A flat tappet lifter face is convex, the cam lobe is slightly tapered (about 0.005-in. 0.007-in.) and the lifter bore is offset to make the lifter rotate during operation. this rotation is essential because it spreads the wear over a greater surface area If the lifter fails to spin, it will destroy itself and its cam lobe.
Tech A says that a flat-tappet hydraulic lifter rotates during operation. Tech B says the face of the lifter should be convex. Who is right.
A. If the piston diameter is smaller than the specified service limits, the piston must be replaced. However when a pin fits loose in the piston, the piston pin bore and connecting rod small end can be resized to fit an oversized wrist pin.
Tech A says that a piston must be replaced if the diameter is smaller than than specification. Tech B says that a piston must be replaced if the wrist pin clearance is greater than specification. Who is right? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
C. Both Technicians A and B
Tech A says that a twisted connecting rod would cause a slanted wear pattern on the side of a piston. Tech B says a bent connecting rod would cause the rod bearing inserts to have more wear on one side. Who is right? A. Tech A B. Tech B C. Both Tech A and Tech B D. Neither Tech A or Tech B
C. A vacuum gauge connected to the intake manifold or a pressure gauge installed in the front oxygen sensor hole can be used to check for a restricted exhaust system. A blockage in an exhaust system can be caused by physical damage, such as a dent in a pipe, a clogged muffler or catalytic converter, or a collapsed exhaust pipe.
Tech A says that a vacuum gauge and pressure gauge can both be used to determine if an exhaust system is restricted. Tech B says the cause of an exhaust system restriction could be a dent in an exhaust pipe, a collapsed exhaust pipe or a catalytic converter. Who is right? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
c. Both Technicians A and B. The oil during engine reassembly to prevent it from cavitating or sucking air during engine start up. To prevent the pickup from sucking air and subsequent oil starvation and engine damage, make sure the pickup screen is positioned close to the bottom of the oil pan to endure it is always submerged in oil.
Tech A says that before installing an oil pump, it should be primed with clean oil. Tech B says that before installing an oil pump, the position of the pickup screen should be checked to make sure it fits closely to the bottom of the oil pan. Who is right? A. Tech A B. Tech B C. Both A and B D. Neither A or B
B. Connecting rod journals typically experience the most wear at TDC (Top Dead Center). Because bearing journals can experience taper wear, barrel wear or hourglass wear, they should be measured at the center and at both ends.
Tech A says that crankshaft connecting rod journals typically experience the most wear at BDC (Bottom Dead Center). Tech B says that bearing journal diameter should be measured at the center and at both ends. Who right? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
B. Some engines use torque to yield head bolts. These bolts are purposely over-stretched when tightened and are not reused. Head bolts should be removed in the sequence specified by the manufacturer, which may or may not be the reverse order of the torque sequence. If a removal sequence is not given, then remove the bolts in reverse order of the torque sequence.
Tech A says that cylinder head bolts should always be loosened in reverse order of the torque sequence. Tech B says that torque to yield head bolts cannot be reused. Who is right? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
A. Tech A is correct because most wear to the engine cylinder is at the top where ring loading is greatest. Tech B is wrong because the difference in bore measurements taken at points parallel and perpendicular to the crankshaft will indicate cylinder bore out of roundness.
Tech A says that engine cylinders wear most at the top of the ring travel. Tech B says that the difference in cylinder bore measurements taken parallel and perpendicular to the crankshaft will indicate cylinder bore taper. Who is right
C. Both will affect valve train geometry Resource: https://www.dragzine.com/tech-stories/engine/engine-tech-understanding-valvetrain-geometry-and-getting-it-right/
Tech A says that excessive cylinder head or block deck resurfacing on a push rod engine can change the geometry between the valve stem tip and rocker arm. Tech B says that excessive grinding of the valve face and seat changes the geometry between the valve stem tip and rocker arm. Who is right? A. Tech A B. Tech B C. Both Tech A and Tech B D. Neither Tech A or Tech B
A new ring can contact the old rounded ring ridge. this will push the bottom part of the thing groove down, possibly affecting the second ring clearance. If the block is to be bored, removal of the ring ridge will not be necessary.
Tech A says that if a ring ridge at the top of the cylinder is not removed, damage to the new piston and rings can result. Tech B says when the block will be bored for oversize pistons, removing the ridge is not necessary. A. Tech A B. Tech B C. Tech A and B D. Neither Tech A or B
C. Either method can be used to check main bearing oil clearance. Resource: http://knowhow.napaonline.com/know-notes-measure-engine-bearing-clearance/
Tech A says that main bearing oil clearance can be checked with Plastigage. Tech B says that main bearing oil clearance can be checked with a dial bore gauge. Who is correct A. Tech A B. Tech B C. Both A and B D. Neither A or B
A. Piston rings are designed with a slight taper on the ring face to scrape oil off the cylinder wall, When installed upside down and off the walls, they scrape oil up into the combustion chamber where it is burned, causing increased oil consumption. Installing the rings upside down does not change the ring land clearance, so the ring lands will not be affected.
Tech A says that piston rings installed upside down will cause will cause increased oil consumption. Tech B says rings installed upside down will cause piston rings land damage. A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or Tech B
D. Neither Tech is right. Tech A is wrong because retarded valve timing will cause the valves to open and close at the wrong time, thereby reducing compression and manifold vacuum readings. Retarded valve timing can be caused by a loose timing belt or chain jumping one or more teeth. Tech B is wrong because a low but steady manifold vacuum reading may be caused by a lean air/fuel mixture. Air leaks or vacuum leaks can cause a lean condition and are common causes of rough idle, hesitation, stalling and hard starting. IF the mixture is artificially enriched by injecting propane into the induction system, an engine running lean should speed up and the vacuum reading should rise.
Tech A says that retarded valve timing can cause high cylinder compression readings. Tech B says that a lean air/fuel mixture can cause a high intake manifold vacuum reading. Who is right? A. Tech A B. Tech B C. Both Tech A and Tech B D. Neither Tech A or Tech B
B. The weights and springs in a centrifugal advance mechanism are calibrated to advance ignition timing as engine speed increases, therefore the engine must be accelerated when checking centrifugal advance. Vacuum advance works only in responses to changes in vacuum applied to the unit, therefore changes in ignition timing can be seen with a timing light while applying vacuum with the engine at idle.
Tech A says that the engine should be accelerated when checking vacuum advance. Tech B says that the engine should be accelerated when checking centrifugal advance. Who is right? A. Tech A B. Tech B C. Tech A and B D. Neither Tech A or B
C. both A and B- Proper surface finish is critical for head gasket sealing. The surface finish must be correct for the type of head gasket that will be used, particularly with multi-layer steel gaskets, or gasket will not seal properly. Refer to the gasket manufacturer's specifications for surface finish requirements. The surface finish can be checked after milling or grinding using a profilometer or comparator gauge. A comparator gauge is a metal card with sample patches of various surface textures to visually compare with the head surface.
Tech A says that the finish left on a cylinder head by a resurfacing machine must be appropriate for the head gasket that will be used. Tech B says that the finish can be checked with a metal card that has sample matches of various surface textures. Who is correct? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
D. On engines with full-floating wrist pins, the retainer clips at the ends of the pin should always be replaced with new ones. Full floating pin bushings that are worn are replaced by pressing them in. Then they are finish honed to provide the correct clearance.
Tech A says that the retainer clips on pistons with floating pins should be reused if they are not damaged. Technician B says that after a full floating pin bushing is pressed into the rod, the piston and rod is then assembled. Who is correct? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
D. There are times when the specific gravity readings will be inaccurate. One is just after adding water to the battery. After adding water, it is recommended to wait at least one day, or until the vehicle has been operated for a while to check the specific gravity. Another time is during or just after charging. After charging, it is recommended to wait at least 15 minutes prior to checking the specific gravity
Tech A says that the specific gravity of the battery electrolyte should be checked after adding water to bring all cells to the proper level. Tech B says the specific gravity of the battery should be checked right after the battery is charged. Who is right? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
D. The thermostats function is to allow the engine to come to operating temperature quickly and then maintain operating temperature. The PCM bases fuel mixture, ignition timing, EGR operation and other functions in part on input regarding coolant temps. Only the correct heat range thermostat should be installed. If the thermostat is good and the engine runs hot, another problem exists.
Tech A says that the thermostat controls maximum engine temperature. Tech B says if the engine continuously runs hot, install a cooler thermostat. Who is right? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
A. Tech B is wrong because tap-in oil gallery plugs are usually used inside the engine. If one came out, it would cause a loss of oil pressure but the oil leak would be inside the engine. Oil gallery plugs on the outside of the engine are most often threaded.
Tech A says that threaded oil gallery plugs can be removed by first heating them up with a torch and then quenching with wax. Tech B says that if a tap in oil gallery plug comes out, oil pressure will be lost and there will be oil all over the outside of the engine. Who is right? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
C. Both Tech A and B- The effect of torque on the fastener changes with friction. Thread lubricants will increase the clamping force provided by a specified torque reading. This could possibly overstretch a fastener. When the threads and the underside of the hex head on the bold are not clean, friction will increase the torque reading, while providing less clamping force.
Tech A says that threads and the underside of the hex head on a bolt must be clean to obtain correct toque. Tech B says that clamping force measured when reading a torque wrench will be changed when using thread lubricants. Who is right? A. Tech A B. Tech B C. Both Tech A and Tech B D. Neither Tech A or Tech B
D. Neither technician is right. Umbrella seals are installed by pushing the sea down on the valve stem until it touches the valve guide boss. It will be positioned correctly the first tome the valve opens. Positive seals are tapped into place on the guide boss during assembly using a special installation tool and a small mallet. Resource: https://www.enginebuildermag.com/1998/07/valve-stem-seals-materials-and-designs/
Tech A says that umbrella valve seals are installed in their operating position during cylinder head assembly. Tech B says that positive valve seals are positioned bu the valve. Who is right?
A. To adjust valve lash for one cylinder's cam lobes, rotate the crankshaft so that its piston is at TDC on the compression stroke. This will position the intake and exhaust valve lifters or OHC cam followers on the base circle of their respective cam lobes. Hydraulic lifters should be adjusted until zero lash is reached, then turned an additional number of turns (3/4 or 1 1/2 turns is typical). The intent is to position the lifter plunger midway in its travel in the lifter body.
Tech A says that valve lash should be adjusted with the piston in the cylinder being adjusted at TDC on the compression stroke. Tech B says that hydraulic lifters should be adjusted to zero lash. Who is right? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
A. On externally balanced engines, the flywheel must be correctly indexed when it is mounted on the crankshaft to maintain engine balance (many flywheels have bolt holes that are unevenly spaced so they can only go on one way). Make certain that index marks are properly aligned when installing the flywheel. Runout on the face of the flywheel is checked with a dial indicator.
Tech A says the flywheel on an externally balanced engine can only be installed in one position on the crankshaft flange. Tech B says that flywheel runout should be checked with a straightedge and feeler gauge.
A. The stem tip height increases with valve or seat grinding. Grinding stem tips can change the stem tip height, but will have no effect on the height, but will have no effect on the valve spring installed height. That measurement is controlled by the height of the keeper grooves above the spring seat of the head. Valve spring installed height is corrected by installing shims between the valve spring and cylinder head.
Technician A says that excessive grinding of valve faces and seats allows the valve tips to move too far away from their spring seats. Technician B says that excessive grinding of the valve face and seat changes the geometry between the valve stem tip and rocker arm. Who is right? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
C. Both Technicians A and B- Exhaust systems can suffer chemical damage causing the components in the system to rot out from the inside. When the engine is started from cold, combustion gases mix with condensation that forms when the hot exhaust contacts the colder exhaust parts, forming acids that corrode the metal. This type of failure is common on vehicles that are driven short distances, since the exhaust system never gets warm enough to evaporate the moisture. To determine chemical damage, tap on the exhaust pipes and muffler with a mallet and listen for rattling or rust breaking loose, which would indicate a problem inside the component. An exception to this would be the catalytic converter when it is struck with a mallet, it means that the ceramic sub straight has come loose and its disintegrating.
Two Technicians are inspecting an exhaust system. When he taps on the muffler with a mallet, Tech A hears noise coming from inside the muffler and says that is most likely rotting out from the inside. Tech B says that this type of failure is due to chemical damage Who is right? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
C. Installing a new valve seat will position the valve lower in the head and reduce stem height. A and B are incorrect because grinding the valve seat will place the valve height in the head and increase the stem height. D is also wrong; shims are used to correct valve spring installed height.
When a cylinder head is disassembled, the stem height on one valve is found to be too high. Which of the following can correct this? A. Regrind the valve B. Regrind the valve seat C. Install a new valve seat D. Install a shim
B. It makes no sense to perform repairs on a cylinder head that might not be able to be usable. The head should first be checked for warpage and cracks. If the top of the head is warped enough to interfere with cam bore alignment and /or restrict free movement of the camshaft, the head must be straightened before it is resurfaced.
When a cylinder head with an overhead camshaft is discovered to be warped, which of the following is the most correct repair option? A. Replace the head B. Check for cracks, straighten the head, resurface the head C. Resurface the head, then straighten it D. Straighten the head, resurface the head, check for cracks
C. Cylinders walls are best cleaned with hot water and a stiff bristle brush. Solvents drive grit deeper into the pores of the cast iron cylinder walls.
When cleaning a a cylinder block for final assembly, which of the following should be used. A. Carburetor cleaner B. Kerosene or cutting lubricant C. Hot, soapy water and a bristle brush D. Petroleum solvent
D. Neither Tech is correct. If a failed exhaust valve was the cause, air would be heard from the exhaust pipe. If the intake valve failed, air would be heard from the carburetor or throttle valve assembly. If bubbles are seen in the radiator coolant, the cause could be a leaking cylinder head gasket or a cracked head or block.
When conducting a cylinder leakage test, bubbles are seen in the coolant in the radiator. Tech A says a failed exhaust valve is the cause. Tech B says a failed intake valve is the cause. Who is right? A. Tech A B. Tech B C. Both Tech A and Tech B D. Neither Tech A or Tech B
C. When performing a leakdown test, if pumping air into a particular cylinder produces bubbles in the radiator coolant, you know that the leak is in that cylinder. The other methods can be used to determine if the engine has an internal coolant leak, but would not identify the leaking cylinder.
Which of the following methods can be used to find a cylinder with an internal coolant leak? A. Draw vapors from the radiator into a vial containing a special chemical and look for a color change. B. Hold an exhaust analyzer probe over the radiator neck and check for the presence of exhaust gasses C. Perform a leak down test and look for the presence of bubbles in the radiator. D. All of the above
C. The valve should be removed from the hose and shaken. If the valve rattles when shaken, it is not stuck open or closed. The hose from the intake manifold to the PCV valve is most likely plugged.
While the engine is running, a technician pulls the PCV valve out of the valve opening and places his finger over the valve. No vacuum is felt. Tech A says that the PCV valve could be stuck closed. Tech B says that the hose between the intake and manifold could be plugged. Who is right? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
