Heating and Cooling Flashcards

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?

Answer: Thermostat stuck open

A thermostat stuck open lets coolant flow through the radiator constantly, so the engine runs cold and heat output drops.

For each 1 psi of pressure a radiator cap holds, the coolant boiling point rises by approximately how much?

Answer: 3°F

Each psi of system pressure raises the boiling point about 3°F, so a 15 psi cap adds roughly 45°F.

A 50/50 mix of ethylene glycol antifreeze and water gives freeze protection down to approximately:

Answer: -34°F

A 50/50 ethylene glycol mix protects to about -34°F.

A technician suspects a head gasket leak into the cooling system. Which test directly detects combustion gases in the coolant?

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).

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?

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.

Coolant is dripping from the small weep hole on a water pump. This indicates:

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.

To check a cooling system for electrolysis, the technician should use a:

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.