ASE Heating and Cooling 4 — Questions and Answers
Question 1: A cooling system holds pressure poorly during a pressure test, but no external leaks can be found. Technician A says the head gasket could be leaking. Technician B says the heater core could be leaking. Who is correct?
- Technician A only
- Technician B only
- Both A and B (Correct answer)
- Neither A nor B
Correct answer: Both A and B
A pressure loss with no visible leak can come from an internal head gasket leak or from a heater core leaking into the cabin.
Question 2: Why is a refractometer preferred over a float-type hydrometer for checking coolant?
- It measures coolant pH directly
- It reads accurately for both ethylene and propylene glycol (Correct answer)
- It detects combustion gases
- It measures system pressure
Correct answer: It reads accurately for both ethylene and propylene glycol
A refractometer gives accurate freeze-point readings for both glycol types, while hydrometers are calibrated for ethylene glycol only.
Question 3: What happens if the coolant mixture is more than about 70% antifreeze?
- Freeze protection keeps improving
- Freeze protection and heat transfer both get worse (Correct answer)
- The boiling point drops below 212°F
- The coolant turns acidic right away
Correct answer: Freeze protection and heat transfer both get worse
Above about 70% glycol, freeze protection actually gets worse and heat transfer drops, which can lead to overheating.
Question 4: Why does the lower radiator hose often have a coiled wire spring inside it?
- To ground the radiator electrically
- To keep the hose from collapsing under water pump suction (Correct answer)
- To filter debris from the coolant
- To reduce vibration noise
Correct answer: To keep the hose from collapsing under water pump suction
The lower hose is on the suction side of the water pump, so the spring keeps it from collapsing at high RPM.
Question 5: What is the typical recommended service interval for long-life OAT coolant?
- 1 year or 12,000 miles
- 2 years or 24,000 miles
- 5 years or 150,000 miles (Correct answer)
- It never needs replacement
Correct answer: 5 years or 150,000 miles
Extended-life OAT coolants are commonly rated for about 5 years or 150,000 miles; always follow the OEM schedule.
Question 6: When pressure testing a cooling system, the test pressure should be:
- Twice the radiator cap rating
- The pressure stamped on the radiator cap, not above it (Correct answer)
- At least 30 psi on every system
- Equal to engine oil pressure
Correct answer: The pressure stamped on the radiator cap, not above it
Testing at the cap's rated pressure finds leaks without risking damage to the radiator, hoses, or heater core.
Question 7: A technician uses a float-type hydrometer to check a propylene glycol coolant. What will the result be?
- An accurate freeze-point reading
- An inaccurate reading because of the different specific gravity (Correct answer)
- A reading of the coolant's pH
- A reading of electrolysis voltage
Correct answer: An inaccurate reading because of the different specific gravity
Propylene glycol has a different specific gravity than ethylene glycol, so a hydrometer reading will be wrong.
ASE Heating and Cooling 4
A cooling system holds pressure poorly during a pressure test, but no external leaks can be found.
Technician A says the head gasket could be leaking.
Technician B says the heater core could be leaking.
Who is correct?