Applicable Systems
CX210 Excavator
Symptoms
The engine ECU reports a high coolant temperature fault. The gauge reads above 107C (225F) and the engine derates to 70% power to protect against thermal damage.
Possible Causes
- Low coolant level due to leakage in the radiator or hoses
- Water pump impeller worn or sheared, reducing coolant circulation
- Radiator core blocked externally by dust, mud, or debris
- Thermostat stuck closed preventing coolant flow through the radiator
Troubleshooting Steps
- Step 1: Check the coolant level in the surge tank and inspect for external leaks
Fill to the COLD FULL line with the correct coolant mixture if low - Step 2: Inspect the radiator core for external blockage
Clean with low-pressure water from the fan side outward; avoid high pressure that damages fins - Step 3: Verify water pump operation by checking the upper radiator hose temperature after warmup
The hose should warm up gradually; if it stays cold, the pump or thermostat may be faulty - Step 4: Test the thermostat by placing it in hot water at 82C (180F)
The thermostat should begin to open at 82-87C; replace if it does not open
How to Reset
Reset: The engine derate clears automatically once coolant temperature drops below 100C. Cycle the key switch to clear the fault code.
Common Replacement Parts
- Thermostat: 82C opening temperature (Match OEM part number for the engine model)
- Water pump assembly: Complete with gasket (Replace coolant when installing new pump)
- Coolant: 50/50 ethylene glycol and deionized water (Use premixed long-life coolant)
Frequently Asked Questions
- Q: What coolant should I use?
Use the OEM-specified heavy-duty diesel coolant. Mixing different coolant types can cause gelling and water pump seal damage.
- Q: How often should the coolant be changed?
Every 2000 hours or 2 years, whichever comes first. Extended-life coolants may last up to 6000 hours.
- Q: Can I run with a slight coolant leak?
No. Even small leaks lead to air pockets in the system, causing hot spots and cylinder head cracking.
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Source: OEM Service Manual
Category: Heavy Equipment
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