AERA Diagnostic & Troubleshooting Methods 5

Question 1

An engine emits white smoke from the exhaust that persists after full warm-up. A chemical combustion gas test of the coolant is positive. What is the MOST appropriate next step?

Accepted Answer

Perform a cylinder leakdown test to identify the affected cylinder(s)

Answer

After confirming combustion gas in the coolant, a cylinder leakdown test pinpoints which cylinder(s) are leaking into the cooling system through a failed head gasket or crack.

Question 2

Which piston ring installation error would MOST likely cause immediate high oil consumption but normal compression on a newly rebuilt engine?

Accepted Answer

Oil control ring expander ends overlapped

Answer

Overlapping the oil control ring expander prevents the ring from exerting proper radial pressure, severely compromising oil scraping and causing immediate high oil consumption.

Question 3

A technician uses a dial bore gauge and finds that a cylinder bore is within wear limits but has 0.003" taper. What is the BEST course of action?

Accepted Answer

Bore or hone the cylinder to remove taper before fitting new rings

Answer

Cylinder taper prevents uniform ring contact throughout the stroke; the cylinder must be bored or honed to correct the taper regardless of whether absolute dimensions are within limits.

Question 4

When inspecting a failed engine, the technician finds the rod bearing on cylinder #3 is severely spun and wiped. The other bearings show normal wear. What is the FIRST question to investigate?

Accepted Answer

Was the correct bearing size installed on that rod?

Answer

An isolated bearing failure at one cylinder most often indicates a local cause such as wrong bearing size, lack of crush, or assembly error—check bearing selection and installation first.

Question 5

What does a vacuum gauge reading that slowly drops from a normal value to a low value and then recovers, in a repeating cycle at idle, indicate?

Accepted Answer

A sticking valve—likely a valve that is intermittently not seating

Answer

A cyclically dropping and recovering vacuum reading at idle is the classic signature of a sticking valve that temporarily holds open and then releases.

(AERA) Automotive Engine Rebuilders Association Certification Practice Test

(AERA) Automotive Engine Rebuilders Association Certification Practice Test

AERA Diagnostic & Troubleshooting Methods 5