| Cause | Correction | |
| Radiator or cab heater leaking |
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Visually inspect the radiator heater, hoses and connections to locate the leak. |
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If oil is present int he coolant, check for a transmission or lube oil cooler leak. |
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| External engine leak |
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Visually inspect the engine and components for seal or gasket leaks. |
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| Overheating or leaking compression gases resulting in loss through the radiator overflow. |
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Review the operation for overheating and low power. Refer to Troubleshooting Logic for Coolant temperature above normal. |
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| If equipped, transmission cooler leak |
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Check for mixing of coolant and transmission fluid. |
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| If equipped with a water cooled air compressor, leaking head or head gasket |
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Look for coolant in the oil. Check/replace head or gasket. |
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| If the engine is aftercooled, aftercooler leak |
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Check/replace the aftercooler. Look for coolant in the intake manifold and in the oil. |
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| Lube oil cooler leak |
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Check/replace the head gasket. |
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| Head gasket leak |
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Check/replace the head gasket. |
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| Cracked or porous head |
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Check/replace the head. |
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| Leak in cylinder block coolant passages |
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Check/replace the cylinder block. |