Analysis of Causes of High Water Temperature in Diesel Generator Sets

Ⅰ. Insufficient cooling water (most common)
1. Radiator water shortage, low coolant level: leaks (pipes, radiator, cylinder gasket, water pump seal leaking), long-term evaporation loss.
2. Incorrect antifreeze mixture: in winter, antifreeze concentration too high, reducing heat dissipation.

Ⅱ. Radiator system blockage/poor heat dissipation
1. Radiator clogged with dust, fluff, oil: external fins clogged, air cooling cannot dissipate heat; internal scale blocks water passages.
2. Radiator fan malfunction:
- Mechanical fan: belt loose/broken, slipping losing rotation;
- Thermo-viscous fan: oil failure prevents engagement, fan does not speed up;
- Electric control fan: thermostat switch or sensor failure, fan does not start.
3. Damaged shroud causing air leakage, hot air returning to the radiator.

Ⅲ. Water circulation failure (water not circulating)
1. Water pump failure: impeller wear, keyway slipping, insufficient water flow; water pump bearing seized.
2. Thermostat stuck closed: cannot open when cold, coolant stays in small loop, does not enter main radiator, water temperature rapidly rises (common fault).
3. Bent pipes, scale blocking engine water passages.

Ⅳ. Engine body and load abnormalities (excessive heat source)
1. Incorrect fuel injection timing, poor fuel atomization, misfiring: severe afterburn, engine block overheating.
2. Long-term overload operation: overloading, sudden load changes, engine overheating due to overload.
3. Blown cylinder gasket: cylinder gases enter water jacket, radiator bubbling, overflow at filler neck, rapid water temperature rise, often accompanied by engine oil emulsification.
4. Exhaust blockage, clogged air filter causing insufficient intake, worsened combustion and heat generation.

Quick and simple troubleshooting sequence
1. Stop the engine and let it cool → check coolant level and for leaks
2. Check if the radiator is dirty and whether the fan is rotating
3. Touch upper and lower hoses to check temperature difference: large difference = thermostat not opening
4. If temperature is still high when running unloaded: check water pump, scale, cylinder gasket, fuel injection