ASE Heating and Cooling 5

Question 1

An infrared thermometer scan of a warm radiator shows several cold vertical bands. What does this indicate?

Accepted Answer

Plugged radiator tubes

Answer

Cold spots across a radiator show tubes with no coolant flow, which usually means internal clogging.

Question 2

When a thermostat is bench-tested in heated water, it should:

Accepted Answer

Start to open near its rated temperature

Answer

A good thermostat starts to open close to its stamped temperature and opens fully about 20°F above it.

Question 3

How should a thermostatic (viscous) fan clutch behave when the engine is at full operating temperature?

Accepted Answer

Lock up more and resist being turned

Answer

A heated bimetal spring engages a viscous clutch, which increases fan speed and resistance when cooling is needed.

Question 4

With the engine running, steady bubbles are seen in the coolant reservoir and coolant is pushed out of the overflow. What is the most likely cause?

Accepted Answer

Head gasket failure or cracked cylinder head

Answer

Combustion gas forced into the cooling system shows up as continuous bubbles and pushes coolant out.

Question 5

How should a thermostat be installed?

Accepted Answer

With the temperature-sensing pellet facing the engine

Answer

The wax pellet has to sit in engine coolant to sense engine temperature, so it faces the engine.

ASE - Automotive Service Excellence Certified Tech Practice Test