C220 Temperature rises from 90c to120c and down to 90c

[Kenwood870]

Hi to all
making my way down from Manchester to Newquay temperature gauge was fluctuating from 90C to 120C and back to 90C and fluctuating in between anybody had this experience car is C220 CDI sport.
Mike ...

 

[Mr Greedy]

My guess would be either you have a coolant leak somewhere that seriously needs addressing and the resultant steam pockets cause wild temperature fluctuations, or the thermostat is shot.

Either was, it should be rock solid at 88-90°C all day long, and operating like this for anything other than very very short periods of time is very likely to utterly toast your engine. Warped block/head etc.

 

[Mr Greedy]

P.S. welcome to the forum Mike

 

[Droverunner]

Yes we had this recently on wife's CLK 220 CDi. It was the coolant temp sender which was failing. Don't leave it like this if it were the same fault as it soon caused a frustrating trip ending with limp home speeds.

Sensor only £15 from Mercedes and easy to fit.

Yours of course could be something else but worth considering the above.

 

[sausage]

My C220 CDI Sport temp was rock solid and did not fluctuate. Good advice above. Do not ignore it. Check your coolant level as well.

I changed a thermostat on a Jeep a few years ago, three screws and lift the cover off, remove the old, insert the new. Re-fit three screws. Of course a different car will be different, the point being, these parts are usually designed to be easily changeable.

 

[M80]

Your 651 engine has a more complicated thermostat / ECU arrangement.
I have seen mine slow to rise, when it is up to temperature it can fluctuate between 72 and 106. It does seem to settle some after many miles.

I changed the stat and it was no better.

120 does seem too high though, how accurate is that?

 

[mersum1es]

As above, ecu opens thermostat in advance when it detects power rise taken from engine. There is a heat element on wax control unit.

 

[mattkh]

Hi to all
making my way down from Manchester to Newquay temperature gauge was fluctuating from 90C to 120C and back to 90C and fluctuating in between

Did this coincide with the car going up a steep hill..???
By the way, how many miles has the engine done?