ASE Heating and Cooling 2 — Questions and Answers
Question 1: A vehicle takes a long time to warm up, the temperature gauge reads low on the highway, and heater output is weak. What is the most likely cause?
- Thermostat stuck closed
- Thermostat stuck open (Correct answer)
- Restricted radiator core
- Faulty radiator cap
Correct answer: Thermostat stuck open
A thermostat stuck open lets coolant flow through the radiator constantly, so the engine runs cold and heat output drops.
Question 2: For each 1 psi of pressure a radiator cap holds, the coolant boiling point rises by approximately how much?
- 1°F
- 3°F (Correct answer)
- 10°F
- 15°F
Correct answer: 3°F
Each psi of system pressure raises the boiling point about 3°F, so a 15 psi cap adds roughly 45°F.
Question 3: A 50/50 mix of ethylene glycol antifreeze and water gives freeze protection down to approximately:
- 0°F
- -15°F
- -34°F (Correct answer)
- -84°F
Correct answer: -34°F
A 50/50 ethylene glycol mix protects to about -34°F.
Question 4: A technician suspects a head gasket leak into the cooling system. Which test directly detects combustion gases in the coolant?
- Cooling system pressure test
- Chemical block (combustion leak) test (Correct answer)
- Electrolysis voltage test
- Refractometer test
Correct answer: Chemical block (combustion leak) test
A block tester draws air from the radiator through a fluid that changes color when it contacts combustion gases (CO2).
Question 5: A customer reports a sweet smell inside the car, a greasy film on the windshield, and a damp passenger floor. What is the most likely cause?
- Leaking heater core (Correct answer)
- Leaking water pump seal
- Stuck blend door
- Plugged A/C evaporator drain
Correct answer: Leaking heater core
A leaking heater core puts coolant into the cabin, which causes a sweet odor, an oily fog on the glass, and wet carpet.
Question 6: Coolant is dripping from the small weep hole on a water pump. This indicates:
- Normal condensation
- A failed internal shaft seal (Correct answer)
- Overpressure from a bad cap
- A loose drive belt
Correct answer: A failed internal shaft seal
The weep hole lets coolant escape when the pump's shaft seal fails, so the pump should be replaced before the bearing is damaged.
Question 7: To check a cooling system for electrolysis, the technician should use a:
- Digital voltmeter with one lead in the coolant and the other on engine ground (Correct answer)
- Ohmmeter across the radiator inlet and outlet
- Test light from the radiator cap to battery positive
- Ammeter in series with the cooling fan
Correct answer: Digital voltmeter with one lead in the coolant and the other on engine ground
A DVOM measures stray voltage between the coolant and ground, and excess voltage points to depleted coolant or a poor ground.
ASE Heating and Cooling 2
A vehicle takes a long time to warm up, the temperature gauge reads low on the highway, and heater output is weak.
What is the most likely cause?