Engine Systems and Repair Flashcards

What tool is used to measure the installed height of a valve spring?

Answer: Vernier caliper or spring height micrometer

A vernier caliper or dedicated spring height micrometer is used to measure the installed height of valve springs from the spring seat to the underside of the retainer.

What is the purpose of the piston pin offset in modern engines?

Answer: To reduce piston slap during the transition from compression to power stroke

The piston pin is offset slightly toward the thrust side to reduce the impact force (piston slap) as the piston transitions from the compression stroke to the power stroke, reducing noise and wear.

A technician measures 0.08 mm (0.003 in.) of main bearing oil clearance. The specification is 0.02–0.05 mm. What action is required?

Answer: Replace the main bearings with the correct undersize

Excessive oil clearance reduces oil pressure and lubrication effectiveness. The bearings must be replaced. If the crankshaft journals are within specification, standard bearings or the correct undersize bearings are installed.

What happens to an interference engine when the timing belt breaks?

Answer: The pistons contact the open valves, causing engine damage

In an interference engine, the valves and pistons occupy the same space at different times. When the timing belt breaks, valves remain open and are struck by the pistons, causing bent valves and potential piston damage.

What is the function of the positive crankcase ventilation (PCV) valve?

Answer: To regulate the flow of crankcase vapours back into the intake for combustion

The PCV valve meters crankcase blow-by gases back into the intake manifold to be burned during combustion, reducing emissions and preventing crankcase pressure buildup.

A technician is checking camshaft endplay. Which measuring tool is most appropriate?

Answer: Dial indicator mounted to the block with the camshaft pushed fore and aft

Camshaft endplay (axial movement) is measured using a dial indicator mounted to the engine block while pushing the camshaft forward and backward to measure the total movement.