ASE A1 Engine RepairLubrication and Cooling SystemsMedium
A customer complains of poor heater performance and the engine running slightly warmer than usual, but not overheating. The coolant level is full and the thermostat was recently replaced. Upon inspection, the technician finds that both heater hoses are warm, but not equally hot. What is the most likely cause?
- AA clogged heater core
- BA faulty blend door actuator
- CA failing water pump
- DAn airlock in the heater core
Show answer & explanationAnswer & explanation
Correct answer: A. A clogged heater core
If both heater hoses are warm but not equally hot, it indicates that coolant is flowing to the heater core, but the core itself is restricted, preventing adequate heat transfer. This restriction leads to poor heater performance and can contribute to the engine running slightly warmer due to reduced overall coolant circulation.
Why the other options are wrong
- B. A faulty blend door actuator would cause poor cabin heat but would not affect the temperature of the heater hoses or cause the engine to run warmer.
- C. A failing water pump would cause more general overheating and affect circulation throughout the entire system, not just the heater core with otherwise full coolant.
- D. An airlock in the heater core would typically cause one hose to be hot and the other cold, or very little heat, but if both are warm and there's a restriction, a clog is more likely.
Clogged Heater Core
A clogged heater core restricts coolant flow, leading to poor cabin heating and a temperature differential between the inlet and outlet heater hoses, indicating inefficient heat transfer.
- Poor or no cabin heat
- Both heater hoses warm, but not equally hot
- Engine may run slightly warmer
Memory trick: Heater's weak, hoses warm? Core's clog causing harm!