CLAAS 7729h – Eng A15: Engine Coolant Temperature Excessively High

The engine coolant temperature has surpassed safe operational limits. This condition triggers an engine protection mechanism by the Engine Control Module (ECM), which includes a reduction in engine power to prevent severe damage. While unverified data suggests a power reduction rate of 20% per minute, automatic engine derating is a standard practice when overheating is detected.

• Arion 640-510 series
• Lexion series
• Dominator series
• Jaguar series
• Comandor
• Renault Ares models

1. 1

   Inspect radiator, intercooler, and hydraulic oil cooler fins for external blockages from dust, chaff, or mud (most common cause).

2. 2

   Verify coolant level in the expansion tank (e.g., check for air in the sight glass on Lexion models) and check coolant condition for contamination.

3. 3

   Check for coolant leaks at the radiator, hoses, water pump weep hole, and engine block.

4. 4

   Inspect cooling system components including the radiator cap pressure holding ability, fan belt tension, and radiator hose condition.

5. 5

   Test the thermostat by feeling the top and bottom radiator hoses as the engine warms up (a cold hose while the block is hot indicates a stuck-closed thermostat).

6. 6

   Inspect the engine coolant temperature sensor wiring and connectors for damage, corrosion, or loose connections (look for related codes P0117 or P0118).

1. 1

   Clean the radiator

   If fins are blocked, use compressed air or a pressure washer from a safe distance to clean all debris from the cooling package.

2. 2

   Address leaks

   Replace any leaking components identified during inspection, such as hoses, the radiator cap, or the water pump.

3. 3

   Replace the thermostat

   If the thermostat is diagnosed as stuck closed, replace it to restore proper coolant circulation to the radiator.

4. 4

   Replace the coolant temperature sensor

   If electrical checks indicate a faulty sensor, ensure the engine is cold and unpressurized. Disconnect the electrical connector, unscrew the old sensor (expecting some spillage), install the new sensor, and reconnect.

5. 5

   Replace the water pump

   If the water pump is leaking from the weep hole or has a failed bearing, replace the water pump assembly.

6. 6

   Refill and bleed the cooling system

   After replacing components, refill with manufacturer-specified coolant. Run the engine with the heater on to circulate coolant and purge air from the system, topping up as necessary.