The radiator temperature bulb that makes the fan work is probably dead, or maybe it's just a blown fuse, still after what you said I would check the water pump and more importantly, the head gasket.
I don't know how much a thermostat for a TS 16v engine is worth but they are usually cheap to buy and relatively easy to change, would get that done too in the meantime.
Hope that the head gasket and water pump are ok, those are expensive to change for what i heard.
If there is anything else we can help you with just let us know
Chris (1987 too haha)
ps.sorry if my english isn't good, not my native language!
Last edited by chris_155v6; 08-01-10 at 00:53.