Engine Repair and Diagnosis Flashcards

How is cylinder bore taper determined?

Answer: Compare bore diameter at the top of ring travel with the bottom of ring travel

Taper is the difference in diameter between the top and bottom of ring travel.

How is piston ring end gap correctly measured?

Answer: With the ring squared in the cylinder bore using a feeler gauge

The ring is pushed square into the bore with a piston and the gap is checked with a feeler gauge.

Crankshaft end play is measured with a dial indicator. Which bearing controls it?

Answer: Thrust bearing

The thrust main bearing has flanges that limit fore-aft crankshaft movement.

At idle, a vacuum gauge needle drops sharply by several inches at regular intervals. What is the most likely cause?

Answer: Burned or leaking valve

Each time the faulty cylinder cycles, its leaking valve causes a regular, repeating vacuum drop.

Which procedure is correct for a cranking compression test?

Answer: Remove all spark plugs, disable ignition and fuel, and hold the throttle wide open

Removing all plugs and opening the throttle allows consistent cranking speed and full air intake.

A combustion leak (block) tester fluid changes from blue to yellow when sampling the radiator. What does this indicate?

Answer: Combustion gases are entering the cooling system

The chemical reacts with CO2 from combustion gases, confirming a head gasket leak or crack.

Why must main bearing caps be reinstalled in their original location and orientation?

Answer: They are line-bored together with the block

Caps are machined as a unit with the block, so swapping them misaligns the bearing bores.