What causes Mercedes engines to overheat in Pakistan’s summer traffic, even with normal coolant levels?

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What causes Mercedes engines to overheat in Pakistan’s summer traffic, even with normal coolant levels?

Some Mercedes owners in cities like Karachi o r Lahore notice engine overheating o r unusually high temperature readings in summer traffic, despite full coolant and proper servicing. Could this be due to a failing fan clutch, weak water pump, o r electronic thermostat issues? Are these symptoms more common in Pakistan due to heat and AC load, o r is there a deeper problem with local maintenance practices?

Talha Kyanii asked on 20 Sep 2025 17:18:59 pm

1 Answer

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Gari Master - on 20 Sep 2025 17:21:49 pm

Common causes seen locally:

Radiator fan o r fan clutch failure — In slow traffic, cooling relies heavily on the fan. If it’s not spinning at full speed, the engine will overheat — especially with AC on.

Thermostat o r temperature sensor malfunction — Modern Mercedes use electronically controlled thermostats that can stick open o r closed.

Water pump wear — After 80,000–100,000 km, the impeller o r bearings can fail, especially in plastic-bodied pumps.

Low-quality o r expired coolant — Cheap coolant can lose effectiveness in extreme heat 40°C, which is common in cities like Multan o r Faisalabad.

What to do:

Confirm the radiator fan runs at full speed when engine gets hot with and without AC.

Replace coolant every 2–3 years with genuine Mercedes coolant o r equivalent.

Replace the thermostat and temperature sensor if overheating starts intermittently.

Flush the radiator and inspect the water pump if overheating continues.