has my themostat failed in open?

[Darkstar]

if its stuck open,and you need the motor,try giving the stat housing a few sharp taps(dont break it in this cold weather.)the spring pressure should close it.but then watch the temps like a hawk ,in case it sticks shut.
usuall not my fault if it blows up disclaimers apply

i did think of trying that, but the thought of an overheat if it did stick put me off.

[mikeonb4c]

bite the bullet and put a new thermostat in ASAP esp. if its age is unknown IMHO. At least it'll force a coolant change (make sure you/the garage know how to bleed it properly) so you won't need to do it for 2yrs. Pity about the cold weather though

[Northern Bongolow]

you could try warming everything up a bit,see if the top hose to the rad,is the same temp as the 2 pipes into the expansion tank,they should be very similar.but if the bottom hose out of the rad is the same as those 3 then the stat is stuck open.
dont run it it for more than 15mins to do this test,no need to rev it much,the results should be quickly apparent.