Temperature issue (bit fresh)

[grounch]

Hi


Winter is here (well, kind of winter, it barely goes under 5°C here) and so are temperature related issues.


Driving normally in the city makes the temp reach around 70/80 when not heavy foot, but goes to the needed 90 when i give some load.
Same with uphills, heats fast when under load.


But the issue comes when i drive for example a few miles road downhill, so mostly let myself roll down without any engine load.
That makes the temp drop to around 75/80 and not goes back up until i rev it again.
The thermostat is supposed to open at 88°C.



Of course i thought it was the thermostat. Changed it (was a Denso, now a Hella, both good brands) but did not solved a thing..


Overally the car behaves fine, heat comes quickly to the vents, drives and idle ok, not really overconsuming.
It's a 2005 3.0d.
Lower coolant hose (from thermostat/pump to the rad) is warm but not as hot as the upper one.
Fan is not going crazy.
Temp gauge is in the middle and sitting there, but i've read it's not perfectly calibated, so i'm reading the temp value from the odb secret menu.

How is it behaving with you guys in winter?

Maybe i'm too obsessed having it working perfectly and 10° doesn't change much after all...
Because i have no idea what could be the issue after changing 2 thermostats.