Customer vehicle · 2018 Mazda CX-5 2.2L Diesel
TEST FIRST.
REPAIR THE ROOT CAUSE.
The vehicle arrived after its engine temperature began rising on longer drives. An intermittent coolant warning and repeated coolant top-ups indicated a cooling-system fault that needed proper testing.
CUSTOMER CONCERN
The customer reported the engine temperature rising during longer drives. A coolant warning appeared intermittently, and the coolant reservoir needed regular top-ups.
INITIAL INSPECTION
A pressure test was carried out on the cooling system. No obvious external coolant leaks were found. Further inspection showed signs of coolant loss, but the source was not immediately visible.
The vehicle was scanned for fault codes and live data was monitored while the engine reached operating temperature.
DIAGNOSIS
Further testing identified poor coolant circulation and excessive cooling-system pressure. The thermostat was operating incorrectly and restricting coolant flow under certain operating conditions.
The thermostat assembly was removed and inspected, confirming the fault before replacement.
REPAIR COMPLETED
- Removed and replaced the faulty thermostat assembly
- Refilled the cooling system with the correct coolant
- Bled the cooling system to remove trapped air
- Pressure-tested the cooling system
- Checked cooling-fan operation
- Completed an extended road test
- Rechecked coolant level and engine operating temperature
VERIFIED RESULT
Following the repair, the engine maintained the correct operating temperature throughout the extended road test. Coolant circulation was restored, and no further overheating or warning messages were present.
CUSTOMER OUTCOME
The customer received a clear explanation of the fault and the completed repair. Testing before replacing components identified the root cause and avoided unnecessary repairs.
Customer name, registration and vehicle-identification details are intentionally excluded.