197 stays in cold map?


Paid Member
2 things Turkie,
1) OEM temperature gauges are not accurate, it's more to let you know "oh no it's about to blow" and "oh no it's too cold"
2) I did same as you, tracked what the needle looked like at what temperature through the OBD, it's not a linear progression from 2nd to 3rd line, as like I said it sat just under the third line (which I agree is 90-92degrees) but it was reading 72-73degrees (on a steady cruise on motorway), but then I coaster coming off at a junction and it dropped to 69 (this was old failing stat) and that got above the 2nd line.
But did same on new stat, it only dropped to 72 from 75.

When the stat fails, it doesn't close perfectly, so it overcools. They're designed to fail "open" to overcool, than fail "closed" and cause overheating, they're a really old design really and haven't changed in so many years (until now with many having electronic stats, even though my 1999 740iL had it lol).

To me it sounds like yours is failing (not totally failed), many people have ran it like that like Nath said above with no problem, but to run correct you need to change it really.


Paid Member
Yea what I did was just to allow people to see the relationship of temperature to the lines for diagnostic purposes I can now from that understand like I said mine is not closing enough to hold 76°+ everyone's will act different lower speeds less cooling from the radiator but as long as you see the drop from cold the thermostat is opening and with a standard thermostat it should be 75° but after the car has crossed the 2nd white line and came back once then it should not go with normal running go back to the white line again. So if you fit an 89° thermostat the low speed fan will be running all the time and you don't hear it over the engine noise and the high speed fan kinks in at 90° so your fan will be on all the time even without aircon operating.