Thomas Cse

Hi everyone, i have a problem and i can't find the solution since like a year... mercedes changed some stuff but still got the problem.. i'm explaining...

I have an A207 E250 211CV, When i am driving at a moment the temp needle going crazy and goes from 84° to 120 then 90 then 85 then 100 etc... in half a sec... and if i'm steel driving it goes finally into the redzone but then goin back at normal... i changed the thermostat.. the thermostat sensor.. now they are telling me it's maybe head gasket but i've no symptomes of head gasket..
I got the feelin like the temp needle going crazy when the vent starts to turns : ON (he's running well..) cause when i activate the air cond the needle goin crazy faster...

here is a short video of the problem.. :
thank's in advance...

WRC-LVR

Make sure to have the coolant system properly filled and then bled

Find and check the coolant sensor. Look for corrosion on the connector or leaks that drip down on to it. Clean and repair any electrical connectors and leaks.

Thomas Cse

i have already changed the coolant sensor... everything is ok... and i have nothing on OBD diag... i guess an elec failure would have told me there is a pbm somewhere... or at least mecede's one would have...

Chevota

I second the check to bleed it. Sounds like a classic case of air in the system.