Phase 1 GTV Spider/TS thermostat opens at 83C.. Temperature gauge should sit just above the 'mystery mark'.
Phase 2 GTV Spider/TS thermostat opens at 87C.. Temperature gauge should sit at just below 90C. mark.
V6 should sit just below 90C
(the opening temperatures are stamped on most thermostat housings). You cannot fit a phase 1 TS thermostat to a phase 2 TS, or the other way round (it's a different animal)..
On all cars the gauge should rise to 90c when the car is in slow moving traffic or stationary, The radiator fan will then cut in at 90C
Thermostats are designed to fail in the open/safe position.. therefore a failed thermostat will usually cause over cooling.. NOT over heating..
The centre calibrations on the gauge are 80C (unmarked) going through 90C(marked) to 100C(unmarked)..
The unmarked calibrations are often referred to as 'Mystery Marks',
It can seem odd because the gauge is non linear, the important bit 80C-90C-100C has been electronically expanded..
Makes it easier to read..
On a lot of other cars this zone on the gauge is painted green.. (the safe zone)..
How quickly the gauge swings from the 'moving temperature' to the 'stationary temperature' depends upon the ambient temperature. Obviously there will be a greater variation on phase 1 TS cars. 83C to 90C.
Alfa obviously addressed the issue, hence the different thermostat and cooling system between phase 1 and phase 2 cars
There's nothing in the manual about this..
A lot of confusion is caused by the non linear gauge, the unmarked calibrations.. And the fact that the gauge is not exactly a finely calibrated test instrument..
Leading to people flapping about it and sometimes replacing thermostats when it is not necessary.
So panic over until next winter..
needs a sticky..
Last edited by seadart; 16-02-12 at 06:54.