C180 W204 Temperature Gauge increases to 120deg on dual carriageway

[beachcomber8832]

Good morning, C180 W204 temperature gauge has started to increase from its normal 90deg to 120deg after drive for about 15mins when driving on an open road (not when standing still). Decreasing speed will see a sudden decrease in the temperature (not a gradual decrease). The temperature stays as 90deg when just letting engine idle (i.e. not moving). NB. The coolant is at correct level. Anyone seen this & have any suggestions as to the likely causes (thermostat; water pump etc.?)?

 

[Plonga]

I am having similar issue - changed Thermostat and temp sensor. Have noticed that Inlet hose to water pump is hot but top hose is stone cold. - Suspect water pump?

 

[DrNick]

If its got the M274 engine then it may well be the vacuum operated fast warm up valve sticking, usually part of the water pump. I think it might be possible to disconnect the actuator and try to manually set it in the open position as a check. Changing the water pump is likely to be difficult. I have the same basic engine in an E250 and it was tricky to get to to replace. Maybe the smaller version that you might have might be less so.
M274 fitted to C180 from 2012 I believe. Different engine before that so can't comment if that's yours!

 

[markjay]

If the thermostat was a cheap and easy swap - at a front of the engine at the top, simple Wahler thermostat - then it's a late M271.

If the thermostat was an expensive part with built in electronics, that required 3 hours labour to replace as it's located at the lower left hand side of the engine, then it's an early M274.

BTW, modern engines have two temp sensors, one connects directly to the ECU and can only be read via the OBDII port, the other is a sender that connects to the gauge. Have you checked the temperature as showing via the OBDII port?

 

[DrNick]

Coolant Issue 120°c+ - w204 c180 coupe 1.6 Petrol 2012 | Engine points to water pump in M271

 

[beachcomber8832]

I am having similar issue - changed Thermostat and temp sensor. Have noticed that Inlet hose to water pump is hot but top hose is stone cold. - Suspect water pump?

Good morning, I similarly had the Thermostat changed, followed by a heat sensor & the problem peraisted. Finally the water pump was changed & the problem was immediately resolved (the garage thought it was sticking).

 

[slipons]

I would start with the least expensive, i.e. replace the thermostat. If that doesn't fix it I would investigate a blocked radiator (has the car car been standing for long periods)? failing that I would replace the water pump.

 

[johnsco]

I would start with the least expensive, i.e. replace the thermostat. If that doesn't fix it I would investigate a blocked radiator (has the car car been standing for long periods)? failing that I would replace the water pump.

If it's a 271 engine, replacing the thermostat is easy and inexpensive

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