i fort i would go out for a drive last night it was all good till i went down the bypass and the engine temp started to drop, i found a layby to check to see if coolant was leaking but it wasn't i presumed the stat was stuck open. i was checking all my levels today and i come across rusty coloured coolant, it isnt thick like mayo its really thin as water should be. can anyone shed some light on this for me, would this have stopped my stat from closing up. hopefully its just time for a service and its not f**ked. any help will be appresheated. cheers