General Engine temperature?

[Brittleware]

Hi all - I recently fitted a new thermostat to our 3003 2.2 hdi Ulysse. The temperature was occasionally falling to about 50 - 60 deg.C, slow warm up and an overshoot to 90 deg before falling back to 80 deg.

But, whilst the new thermostat has made warm up faster and no drop in temperature, the guage now varies between 80 and 88, seemingly depending on power output. Is this normal? I would like a constant 83, as that's what the stat says on it!

 

[avionista]

I'm no expert on this matter, but I believe the temperature marking on a wax thermostat indicates the temperature at which it begins to open. It then continues to open wider as the water temperature increases and will be fully open about 12 degrees above its rated temperature. So, your thermostat should start to open at 83C and be fully open at around 95C. There is bound to be some mechanical and thermal lag in a cars cooling system, which may explain the temperature swing you are seeing. If the temperature swing is related to power changes it could be that your radiator thermostat/electric fan operation is not functioning correctly.

 

[Brittleware]

Or a possible restriction in one of the hoses - or the radiator? When we first had the car almost exactly a year ago the temperature never varied from 80 degrees. My wife's Proton Mitsu thingy also holds an absolutely constant temperature. I'll drain the Ulysse and do a back flush I think.