ASE A1 Engine Repair Practice Test
36. An engine's aluminum thermostat housing has corroded prematurely and is leaking coolant. Which of the following is MOST likely causing this condition?
- A. Engine overheating.
- B. Electrolysis.
- C. A leaking radiator hose.
- D. A faulty thermostat.
Answer A is wrong. Overheating an engine can be catastrophic, quickly warping the cylinder head and blowing the head gasket; this damage results in gases and compression leaking from the compression chamber.
Answer B is correct. Electrolysis causes corrosion of dissimilar metals in a cooling system. As the engine coolant breaks down, it becomes acidic. It acts as a catalyst for electrical current. A small amount of electrical current can flow through the coolant corroding the lesser metal, often an aluminum part like the water pump or the engine's coolant outlet.
Answer C is wrong. A loose radiator cap causes an engine to overheat.
Answer D is wrong. An engine with a stuck open thermostat takes too long to reach operating temperature. It can cause unwanted hot spots. A stuck closed thermostat causes an engine to overheat.
37. An engine is losing coolant. A radiator pressure tester is installed on the neck of the radiator while the engine is cold. After starting the engine, the pressure on the gauge quickly rises to 19 psi. Which of the following is causing this test result?
- A. Acidic engine coolant.
- B. The cylinder head gasket is leaking.
- C. There's an air pocket in the cooling system.
- D. This pressure is normal.
Answer A is wrong. Acidic coolant results in corrosion and premature component wear.
Answer B is correct. Aluminum heads warp from overheating; cracks can form in the cylinder head or the engine block. A leaking head gasket allows combustion into the coolant jacket, increasing system pressure. Coolant leaking into the combustion chamber burns white and results in white-gray exhaust smoke.
Answer C is wrong. A stubborn air pocket can prevent engine cooling fan operation and result in overheating. It would not result in a sudden rise in pressure.
Answer D is wrong. This pressure is not normal.
38. All of the following statements are true about an engine's PCV system EXCEPT:
- A. A stuck closed PCV valve results in excessive crankcase pressure.
- B. A stuck open valve or leaking PCV hose results in drivability issues like surging.
- C. Oil leakage indicates a problem with the system.
- D. The PCV valve is a two-way valve that provides a path for blowby gas to flow back into the crankcase.
Answer A is wrong. A stuck closed PCV valve causes excessive crankcase pressure resulting in oil to leaking past seals and gaskets.
Answer B is wrong. A stuck open PCV valve or leaking hose results in a large vacuum leak, a rough idle and drivability issues like surging.
Answer C is wrong. Check around these fittings for any signs of oil. Everything must be tight. Oil leakage indicates a problem with the system.
Answer D is correct. The PCV system is a one-way system that allows blowby gas from the crankcase to flow into the intake manifold for combustion. It helps keep the crankcase and engine oil clean.
39. After setting the hydraulic lifters to zero lash, the engine runs rough and stumbles. Technician A says these lifters require a preload. Technician B says the adjusting nuts should be tightened further. Who is correct?
- A. Technician A
- B. Technician B
- C. Both A and B
- D. Neither A or B
Answer A is correct. It is common to adjust the valves when tuning or after replacing the cylinder head. Hydraulic lifters require a preload adjustment.
Answer B is wrong. There should be a little resistance turning the pushrod when its set to zero lash.
Answer C is wrong. Both technicians are correct. This procedure provides the proper preload for the lifter, pushrod, and rocker arm. A manufacturer may recommend 1/2 turn past zero lash.
Answer D is wrong. Most engine noises are the result of excessive clearances caused by wearing or worn components. The same is true for valve train wear.
40. After removing the valve springs from a cylinder head, they should be checked for:
- A. Squareness with a square and a feeler gauge.
- B. Valve spring installed height with a ruler.
- C. Both A and B.
- D. Neither A or B.
Answer A is correct. Use a square and a flat surface to check valve spring squareness. Rotate the valve and make sure all the coils contact the square as it is rotated. Use a square and a feeler gauge to check for tolerance.
Answer B is wrong. The installed height is measured with the valve spring installed in the cylinder head. The valve springs installed height is measured from the spring's pocket in the head to the bottom of the retainer.
Answer C is wrong. A weak or worn valve spring results in valve float. Valves open and close at incredible speeds; a valve spring must be able to endure these extreme conditions. Valve float can result in damage to other components in the valve train.
Answer D is wrong. Valve float can result in damage to other components in the valve train.