water temp fluctuating


week ago as also today have to travel @ on highway not a far away, not in hurry set the cc to 100 mph / 160 kph and was surprised once the water was almost all the time running between 80-92 C, all the way up and down over and over
any idea why what can be wrong ? as there wasn’t any error code reading...
Is the reservoir at proper level? does it require daily fills and is there a subtle pressure release when removing the reservoir cap when cold?
Are you saying .5 liters or 5 liters of coolant in the last 8 months, any sweet smelling exhaust and white billowy clouds out the exhaust
Also possible the temperature sensor is defective, But think it is a coolant level issue


last 1-2 weeks I think when I am in garage can smell something "other, different form normal" think since roughly the time, when I saw the temp on highway running up & down on highway first time, about the smoke not sure…
Do you think is better to park the car at MB dealer, and wait till the bolts will be fixed, and don’t trying the luck any more ?
Thank you for your help.
Head bolt breakage would cause a sudden lose of coolant, when the car is shut down then the 15 or 16 psi( pressure) that the coolant system runs under would push coolant into the offending cylinder, so large amounts of coolant would be needed, and also large clouds of smoke.
You are using anti freeze and not just plain water, right.


I dead read the M156 head bolt issue thread ,as also searched for other threads like this, just this temp gauge last 2 times on higway really confused me...
hope the bolts will be replaced soon, and all will be good...
Trending Topics


The Best of Mercedes & AMG
For me, it was 165.000km and the guys at the shop said it was very long for a water pump in a heavily abused car.


Did your impeller fall off? or pump seal leak out coolant and cause the overheat issue.
Your mechanic is blowing smoke. Did he also change out the thermostat with the water pump?


To the OP can you be a little more specific about the temp rise, what is the actual temp when this happens. Is the check engine light on or does it come on then go off later when you drive.?






