Mercedes-Benz W140 engine overheats
600 S400 SEL
W140 runs hot, when is a temperature rise normal?
A momentary rise is normal if the temperature drops in under 5 minutes. If the gauge stays constantly above 90 °C, for example in city driving, there is a fault in the cooling system.
What usually causes W140 overheating?
The most common causes are a faulty fan viscous clutch, a slowly opening thermostat, a clogged radiator and a faulty expansion tank cap that lets coolant out. The cause is found and the fault is fixed by replacing the part.
How is the cooling system bled after a coolant change?
Set the heater control to full heat and keep the engine at raised revs. Add coolant until the level no longer drops. The air may only escape over several rounds.
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